XT-8000S Product Specification and OEM Technical Manual Document 1015586 Revision B July 1989 REVISION RECORD Revision Date Published Revised Contents 01 April 1988 Preliminary 02 August 1988 Preliminary 03 September 1988 Preliminary A October 1988 Formal Release A (Adden 1) April 1989 Formal Release B July 1989 Formal Release B (Adden 1) January 1990 Formal Release Document Number: 1015586 WARRANTY Maxtor warrants the XT-8000S Family disk drives against defects in materials and workmanship for a period of twelve months, for the original purchaser. Direct any questions regarding the warranty to your Maxtor Sales Representative. Maxtor maintains Customer Service Centers for the repair and reconditioning of all Maxtor products. Direct all requests for repair to the Maxtor Service Center in San Jose. This assures you of the fastest possible service. REGULATORY APPROVALS UL Recognition obtained: File Number E87276 (S) CSA Certification obtained: File Number LR54048-6 VDE Recognition obtained: File Number 37230G Address comments concerning this manual to: Maxtor Corporation Technical Publications 211 River Oaks Parkway San Jose, California 95134 Telephone: (408) 432-1700 Telex: 171074 FAX: (408) 434-6469 Technical Data Restrictions In case of sale to or use of units by DoD, use, duplication or disclosure of any software, firmware or related documentation is subject to restrictions stated in paragraph (c) (1) (ii) of the Rights in Technical Data and Computer Software clause at DFAR 252.227-7013. For Civilian Agencies: Use, reproduction, or disclosure of the software and related documentation is subject to restrictions set forth in FAR 52.227-19. Unpublished rights reserved under the copyright laws of the United States. Maxtor Corporation, 211 River Oaks Parkway, San Jose, CA 95134. Copyright Notice This manual and all material contained in it are copyrighted. The manual may not be copied, in whole or in part, without the written consent of Maxtor Corporation. The contents of this manual may be revised without prior notice. © Copyright 1988 by Maxtor Corporation, San Jose, California, USA. All rights reserved PREFACE Maxtor reserves the right to make changes and/or improvements to its products without incurring any obligation to incorporate such changes or improvements in units previously sold or shipped. Maxtor publishes descriptive brochures and data sheets, a quick reference guide, and this OEM manual for each product line. Changes that affect the content of any manual are covered by publishing an addendum or revising the affected manual. XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS PREFACE.....................................................V 1.0..............................................INTRODUCTION 1 1.1.....................................General Description 1 1.2.................................Key Disk Drive Features 2 1.3.................................Key Controller Features 2 1.4......................Summary of Supported SCSI Commands 4 2.0.....................................SPECIFICATION SUMMARY 5 2.1..............................Performance Specifications 5 2.2...............................Functional Specifications 6 2.3............................Environmental Specifications 6 2.4.................................Physical Specifications 7 2.5..............................Reliability Specifications 7 2.6.......................Error Rates at the SCSI Interface 8 2.7...................................DC Power Requirements 8 2.8...............................Standards and Regulations 9 3.0................................FUNCTIONAL CHARACTERISTICS 11 3.1.............................General Theory of Operation 11 3.2......Read/Write Control and SCSI Controller Electronics 11 3.3....................................Disk Drive Mechanism 12 Doc 1015586, Rev B ix Maxtor Corporation Doc 1015586, Rev B ix Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 3.4...................................Air Filtration System 12 3.5..............................Head Positioning Mechanism 13 3.6..............................Read/Write Heads and Disks 14 3.7.................................Track and Sector Format 15 3.8..........................................SCSI Interface 16 3.8.1....................Initiator-Target Configurations 16 3.8.2..............Logical/Electrical Signal Definitions 18 3.8.3.......Pin Assignments and Connector (Single Ended) 19 3.8.4.......Pin Assignments and Connector (Differential) 20 3.9..............................Electrical Power Interface 23 3.9.1..................................Power-Up Sequence 24 3.9.2....................................Power Connector 25 3.9.3.......................Frame (HDA) Ground Connector 25 3.10..............................Mounting and Installation 25 3.11...............................................Shipping 29 4.0...................................USER SELECTABLE OPTIONS 31 4.1.......................................SCSI ID Selection 32 4.2..................................Drive Power-Up Options 33 4.3..............................Terminator Power Selection 34 4.4....................................Write Protect Option 35 4.5...........................................Parity Option 35 4.6...........................................Other Jumpers 35 4.7.............................................Sector Size 35 4.8...................................Interface Termination 35 Doc 1015586, Rev B x Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 4.9.....................................Auxiliary Connector 36 4.10........................Spindle Synchronization Control 38 5.0...................................LOGICAL CHARACTERISTICS 39 5.1..................................Power Up and BUS RESET 39 5.1.1.................................Self-Test Sequence 39 5.1.2............................Initialization Sequence 40 5.1.3.................................Self Configuration 41 5.1.4...........................UNIT ATTENTION Condition 41 5.2........................................Buffering Scheme 41 6.0..................................SCSI PHASES AND MESSAGES 43 6.1..........................................BUS FREE Phase 44 6.2.......................................ARBITRATION Phase 45 6.3.........................................SELECTION Phase 45 6.4.......................................RESELECTION Phase 46 6.5.............................Information Transfer Phases 47 6.5.1..................Asynchronous Information Transfer 48 6.5.2..........................Synchronous Data Transfer 48 6.5.3......................................COMMAND Phase 49 6.5.4........................DATA IN and DATA OUT Phases 50 6.5.5.......................................STATUS Phase 50 6.5.6......................................MESSAGE Phase 52 6.6...........................................SCSI Messages 52 6.6.1...................................MESSAGE IN Phase 52 Doc 1015586, Rev B xi Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 6.6.2..................................MESSAGE OUT Phase 53 6.6.3.............................COMMAND COMPLETE (00h) 53 6.6.4............................SAVE DATA POINTER (02h) 54 6.6.5.............................RESTORE POINTERS (03h) 54 6.6.6...................................DISCONNECT (04h) 54 6.6.7.....................INITIATOR DETECTED ERROR (05h) 54 6.6.8........................................ABORT (06h) 55 6.6.9...............................MESSAGE REJECT (07h) 55 6.6.10................................NO OPERATION (08h) 55 6.6.11........................MESSAGE PARITY ERROR (09h) 55 6.6.12.....................LINKED COMMAND COMPLETE (0Ah) 56 6.6.13.........LINKED COMMAND COMPLETE (WITH FLAG) (0Bh) 56 6.6.14............................BUS DEVICE RESET (0Ch) 56 6.6.15................................IDENTIFY (C0h/80h) 56 6.6.16...SYNCHRONOUS DATA TRANSFER REQUEST Message (01h) 57 6.7........................................Error Conditions 59 6.7.1.....................MESSAGE OUT Phase Parity Error 59 6.7.2.........................COMMAND Phase Parity Error 60 6.7.3........................DATA OUT Phase Parity Error 60 6.7.4...........................Initiator Detected Error 60 6.7.5...................................REJECTED Message 61 6.7.6.....................Initiator MESSAGE PARITY ERROR 62 6.7.7...............................RESELECTION Time-Out 62 6.7.8.........................Internal Controller Errors 62 Doc 1015586, Rev B xii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 7.0.................................SCSI COMMAND DESCRIPTIONS 63 7.1...................................SCSI Command Overview 63 7.2.............................................FORMAT UNIT 68 7.2.1.............................Defect List Management 69 7.2.2....................................SCSI Deviations 70 7.2.3.................................Command Parameters 70 7.2.4.......................................Format Modes 72 7.2.5..............................Initiator Defect List 77 A..................................D List Block Format 78 B.......................D List Bytes from Index Format 79 C........................D List Physical Sector Format 80 7.2.6...................................Error Conditions 82 7.3.................................................INQUIRY 84 7.3.1....................................SCSI Deviations 84 7.3.2.................................Command Parameters 84 7.3.3........................................Data Format 85 7.4.............................................MODE SELECT 89 7.4.1....................................SCSI Deviations 90 7.4.2.................................Command Parameters 90 7.4.3..............................Parameter List Format 91 A.........................Parameter List Header Format 91 B...............Parameter List Block Descriptor Format 92 C...................................Page Header Format 93 7.4.4.....................Error Recovery Parameters Page 94 7.4.5..........................Disconnect-Reconnect Page 101 Doc 1015586, Rev B xiii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 7.4.6.................................Format Device Page 102 7.4.7..........Rigid Disk Drive Geometry Parameters Page 105 7.4.8.......................................Caching Page 107 7.4.9..........................Maxtor Drive Control Page 109 7.4.10...........................Read-Ahead Control Page 110 7.4.11..................................Error Conditions 111 7.5..............................................MODE SENSE 114 7.5.1....................................SCSI Deviations 115 7.5.2.................................Command Parameters 115 7.5.3..............................Parameter List Format 117 A.........................Parameter List Header Format 118 B...............Parameter List Block Descriptor Format 119 C...................................Page Header Format 120 7.5.4.....................Error Recovery Parameters Page 120 7.5.5...............Disconnect/Reconnect Parameters Page 123 7.5.6........Direct-Access Device Format Parameters Page 125 7.5.7..........Rigid Disk Drive Geometry Parameters Page 128 7.5.8.......................................Caching Page 130 7.5.9..........................Maxtor Drive Control Page 132 7.5.10................Read-Ahead Control Parameters Page 134 7.5.11..................................Error Conditions 135 7.6....................................................READ 136 7.6.1....................................SCSI Deviations 136 7.6.2.................................Command Parameters 136 7.6.3...................................Error Conditions 137 Doc 1015586, Rev B xiv Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 7.7.........................................READ (EXTENDED) 138 7.7.1....................................SCSI Deviations 138 7.7.2.................................Command Parameters 138 7.7.3...................................Error Conditions 139 7.8.............................................READ BUFFER 140 7.8.1....................................SCSI Deviations 140 7.8.2.................................Command Parameters 140 7.8.3......................................Command Usage 141 7.8.4........................................Data Format 141 7.8.5...................................Error Conditions 142 7.9...........................................READ CAPACITY 143 7.9.1....................................SCSI Deviations 143 7.9.2.................................Command Parameters 143 7.9.3........................................Data Format 144 7.9.4...................................Error Conditions 145 7.10.......................................READ DEFECT LIST 146 7.10.1...................................SCSI Deviations 146 7.10.2................................Command Parameters 146 7.10.3............................................Header 148 7.10.4......................................Block Format 149 7.10.5...........................Bytes from Index Format 150 7.10.6............................Physical Sector Format 151 7.10.7..................................Error Conditions 152 7.11..............................................READ LONG 153 7.11.1...................................SCSI Deviations 153 Doc 1015586, Rev B xv Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 7.11.2................................Command Parameters 153 7.11.3..................................Error Conditions 154 7.12.....................................READ LONG (SCSI-2) 155 7.13.........................READ MANUFACTURERS DEFECT LIST 157 7.13.1...................................SCSI Deviations 157 7.13.2................................Command Parameters 157 7.13.3.......................................Data Format 158 7.14.........................................REASSIGN BLOCK 160 7.14.1...................................SCSI Deviations 160 7.14.2................................Command Parameters 160 7.14.3................................Defect List Format 161 7.14.4..................................Error Conditions 162 7.15.............................RECEIVE DIAGNOSTIC RESULTS 163 7.15.1...................................SCSI Deviations 163 7.15.2................................Command Parameters 163 7.15.3.......................................Data Format 164 7.15.4..................................Error Conditions 164 7.16...........................................RELEASE UNIT 165 7.16.1...................................SCSI Deviations 165 7.16.2................................Command Parameters 165 7.16.3..................................Error Conditions 166 7.17..........................................REQUEST SENSE 167 7.17.1...................................SCSI Deviations 167 7.17.2................................Command Parameters 167 7.17.3.......................................Data Format 168 Doc 1015586, Rev B xvi Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS A........................Nonextended Sense Data Format 169 B...........................Extended Sense Data Format 169 C..........................................Sense Codes 175 7.17.4..................................Error Conditions 179 7.18...........................................RESERVE UNIT 180 7.18.1...................................SCSI Deviations 180 7.18.2................................Command Parameters 180 7.18.3..................................Error Conditions 181 7.19............................................REZERO UNIT 182 7.19.1...................................SCSI Deviations 182 7.19.2................................Command Parameters 182 7.20...................................................SEEK 183 7.20.1...................................SCSI Deviations 183 7.20.2................................Command Parameters 183 7.20.3..................................Error Conditions 184 7.21........................................SEEK (EXTENDED) 185 7.21.1...................................SCSI Deviations 185 7.21.2................................Command Parameters 185 7.21.3..................................Error Conditions 186 7.22........................................SEND DIAGNOSTIC 187 7.22.1...................................SCSI Deviations 187 7.22.2................................Command Parameters 187 7.22.3..................................Error Conditions 189 7.22.4.......................................Subcommands 190 A..........................GET DRIVE STATUS Subcommand 190 Doc 1015586, Rev B xvii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS B........................PASS DRIVE COMMAND Subcommand 192 C...............................READ HEADER Subcommand 195 7.23........................................START/STOP UNIT 198 7.23.1...................................SCSI Deviations 198 7.23.2................................Command Parameters 198 7.23.3..................................Error Conditions 199 7.24........................................TEST UNIT READY 200 7.24.1...................................SCSI Deviations 200 7.24.2................................Command Parameters 200 7.24.3..................................Error Conditions 200 7.25.................................................VERIFY 201 7.25.1...................................SCSI Deviations 201 7.25.2................................Command Parameters 201 7.25.3..................................Error Conditions 202 7.26..................................................WRITE 203 7.26.1...................................SCSI Deviations 203 7.26.2................................Command Parameters 203 7.26.3..................................Error Conditions 204 7.27.......................................WRITE (EXTENDED) 205 7.27.1...................................SCSI Deviations 205 7.27.2................................Command Parameters 205 7.27.3..................................Error Conditions 206 7.28.......................................WRITE AND VERIFY 207 7.28.1...................................SCSI Deviations 207 7.28.2................................Command Parameters 207 Doc 1015586, Rev B xviii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS 7.29...........................................WRITE BUFFER 209 7.29.1...................................SCSI Deviations 209 7.29.2................................Command Parameters 209 7.29.3.......................................Data Format 210 7.29.4..................................Error Conditions 211 7.30.............................................WRITE LONG 212 7.30.1...................................SCSI Deviations 212 7.30.2................................Command Parameters 212 7.30.3..................................Error Conditions 213 7.31....................................WRITE LONG (SCSI-2) 214 APPENDIX A: THE READ-AHEAD FEATURE.......................217 What is Read-Ahead?.....................................217 How Does it Work?.......................................217 Key Read-Ahead Parameters...............................219 Controlling the Read-Ahead Feature......................220 Read Algorithm..........................................220 Read-Ahead Performance..................................220 APPENDIX B: DISCONNECT/RECONNECT CONDITIONS..............223 APPENDIX C: DEFECT MANAGEMENT............................225 Reassignment Sequences..................................226 Cylinder-Oriented Reassignment Sequence..............226 Track-Oriented Reassignment Sequence.................228 Disk Drive-Oriented Reassignment Sequence............228 Host Defect Management Sequence......................229 Defect Management Assumptions and Statistics............229 APPENDIX D: CDB BIT DEFINITIONS..........................233 APPENDIX E: UNITS OF MEASURE.............................235 APPENDIX F: BUFFER RATIO APPLICATIONS....................237 What are the Buffer Ratios?.............................237 Doc 1015586, Rev B xix Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLE OF CONTENTS What are the Performance Benefits from Buffer Ratios?...237 Buffer Full Ratio.......................................237 Buffer Empty Ratio......................................239 What value should be used for the Buffer Ratios?........239 GLOSSARY..................................................241 Doc 1015586, Rev B xx Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual FIGURES XT-8000S Product Specification & OEM Technical Manual FIGURES Figure 3o1..............................Air Filtration System 13 Figure 3o2.........................Head Positioning Mechanism 14 Figure 3o3.......................................Track Format 15 Figure 3o4........................Typical SCSI Configurations 17 Figure 3o5............Connector Locations, Rear View of Drive 22 Figure 3o6...............................SCSI Cable Connector 23 Figure 3o7...................Motor Start Current Requirements 24 Figure 3o8.......................................J3 Connector 25 Figure 3o9.............Mechanical Outline, Top and Side Views 27 Figure 3o10................Mechanical Outline, Isometric View 28 Figure 3o11...............................Removable Faceplate 29 Figure 4o1..................PCB Layout (Single Ended Version) 31 Figure 4o2..........................PCB Layout (Differential) 32 Figure 6o1..............Signal Sequence Chart for SCSI Phases 44 Figure 7o1...............Flow Chart of Automatic Reallocation 97 Figure Ao1................Sequential Reads without Read-Ahead 218 Figure Fo1.......Data Transfer Rate Without Buffer Full Ratio 238 Figure Fo2..........Data Transfer Rate With Buffer Full Ratio 239 XT-8000S Product Specification & OEM Technical Manual TABLES XT-8000S Product Specification & OEM Technical Manual TABLES Table 2o1..........................Performance Specifications 5 Table 2o2...........................Functional Specifications 6 Table 2o3................................Environmental Limits 7 Table 2o4.................................Physical Dimensions 7 Table 2o5..........................Reliability Specifications 8 Table 2o6.........................................Error Rates 8 Table 2o7...............................DC Power Requirements 9 Table 3o1...............Data Field Size vs. Sectors per Track 16 Table 3o2............Connector Pin Assignments (Single Ended) 20 Table 3o3............Connector Pin Assignments (Differential) 21 Table 4o1.....................................SCSI ID Jumpers 33 Table 4o2.........................Summary of Power-Up Options 34 Table 4o3.................Auxiliary Connector Pin Assignments 37 Table 4o4.............Remote SCSI ID Programming Combinations 38 Table 4o5..................................J6 Pin Assignments 38 Table 6o1........................Signal States and Bus Phases 43 Table 6o2.....................................SCSI Bus Timing 47 Table 6o3.........................................Status Byte 50 Table 6o4........................................Status Codes 51 Table 6o5.......................................Message Codes 52 Table 6o6..............................IDENTIFY Message Codes 57 Table 6o7.......SYNCHRONOUS DATA TRANSFER REQUEST Byte Values 58 Table 6o8....Drive Responses to the SYNCHRONOUS DATA TRANSFER REQUEST Message............................................58 Doc 1015586, Rev B xxii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLES Table 7o1.....................Typical CDB for 6-Byte Commands 63 Table 7o2....................Typical CDB for 10-Byte Commands 64 Table 7o3...........................CDB Operation Code Format 65 Table 7o4.................................CDB Operation Codes 65 Table 7o5........................................Control Byte 66 Table 7o6.....................................FORMAT UNIT CDB 71 Table 7o7......................FORMAT UNIT Defect List Header 73 Table 7o8...................Initialization Pattern Descriptor 74 Table 7o9.....................Initialization Pattern Modifier 75 Table 7o10........................Initialization Pattern Type 75 Table 7o11.....................FORMAT UNIT Drive Format Modes 77 Table 7o12.........................FORMAT UNIT D List Formats 78 Table 7o13.....FORMAT UNIT Defect Descriptor(s), Block Format 79 Table 7o14.FORMAT UNIT Defect Descriptor(s), Bytes from Index Format 80 Table 7o15..FORMAT UNIT Defect Descriptor(s), Physical Sector Format 81 Table 7o16........................................INQUIRY CDB 84 Table 7o17..............................INQUIRY Response Data 86 Table 7o18................................MODE SELECT Command 90 Table 7o19..................MODE SELECT Parameter List Header 92 Table 7o20.MODE SELECT Parameter List Block Descriptor Format 93 Table 7o21.............................MODE SELECT Page Codes 94 Table 7o22..................Error Recovery Page (Page Code 1) 95 Table 7o23...................MODE SELECT Error Recovery Modes 100 Table 7o24..........................Disconnect-Reconnect Page 101 Table 7o25.................................Format Device Page 103 Doc 1015586, Rev B xxiii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLES Table 7o26...MODE SELECT Rigid Disk Drive Geometry Parameters (Page Code 4).............................................106 Table 7o27.......................................Caching Page 108 Table 7o28..........................Maxtor Drive Control Page 109 Table 7o29............Read-Ahead Control Page (Page Code 38h) 111 Table 7o30.................................MODE SENSE Command 115 Table 7o31.....................MODE SENSE Page Control Fields 116 Table 7o32..............................MODE SENSE Page Codes 117 Table 7o33...................MODE SENSE Parameter List Header 118 Table 7o34..MODE SENSE Parameter List Block Descriptor Format 119 Table 7o35..................MODE SENSE Page Header Page Codes 120 Table 7o36.MODE SENSE Error Recovery Parameters (Page Code 1) 121 Table 7o37.MODE SENSE Disconnect/Reconnect Control Parameters (Page Code 2).............................................124 Table 7o38..MODE SENSE Direct-Access Device Format Parameters (Page Code 3).............................................126 Table 7o39....MODE SENSE Rigid Disk Drive Geometry Parameters (Page Code 4).............................................129 Table 7o40.................MODE SENSE Default Number of Heads 130 Table 7o41.......................................Caching Page 131 Table 7o42..........................Maxtor Drive Control Page 132 Table 7o43......Read-Ahead Control Parameters (Page Code 38h) 134 Table 7o44...........................................READ CDB 136 Table 7o45................................READ (EXTENDED) CDB 138 Table 7o46....................................READ BUFFER CDB 140 Table 7o47.................................READ BUFFER Header 142 Table 7o48..................................READ CAPACITY CDB 144 Table 7o49..........................READ CAPACITY Data Format 145 Table 7o50...............................READ DEFECT LIST CDB 146 XT-8000S Product Specification & OEM Technical Manual TABLES Table 7o51...............READ DEFECT LIST Defect List Formats 148 Table 7o52............................READ DEFECT LIST Header 149 Table 7o53READ DEFECT LIST Defect Descriptor(s), Block Format 150 Table 7o54..READ DEFECT LIST Defect Descriptor(s), Bytes from Index Format..............................................151 Table 7o55....READ DEFECT LIST Defect Descriptor(s), Physical Sector Format.............................................152 Table 7o56......................................READ LONG CDB 154 Table 7o57..................................READ LONG Command 155 Table 7o58.................READ MANUFACTURERS DEFECT LIST CDB 158 Table 7o59..READ MANUFACTURERS DEFECT LIST Defect Descriptors Returned Format...........................................159 Table 7o60.................................REASSIGN BLOCK CDB 161 Table 7o61..................REASSIGN BLOCK Defect List Header 161 Table 7o62................REASSIGN BLOCK Defect Descriptor(s) 162 Table 7o63.....................RECEIVE DIAGNOSTIC RESULTS CDB 163 Table 7o64...................................RELEASE UNIT CDB 165 Table 7o65..................................REQUEST SENSE CDB 168 Table 7o66........REQUEST SENSE Nonextended Sense Data Format 169 Table 7o67.........................Extended Sense Data Format 170 Table 7o68................................Field Pointer Bytes 172 Table 7o69...........................Actual Retry Count Bytes 172 Table 7o70...................Format Progress Indication Bytes 173 Table 7o71.............REQUEST SENSE Extended Sense Key Codes 174 Table 7o72.............................Additional Sense Codes 176 Table 7o73...................................RESERVE UNIT CDB 181 Table 7o74....................................REZERO UNIT CDB 182 Table 7o75...........................................SEEK CDB 183 Doc 1015586, Rev B xxv Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual TABLES Table 7o76................................SEEK (EXTENDED) CDB 186 Table 7o77................................SEND DIAGNOSTIC CDB 188 Table 7o78............SEND DIAGNOSTIC Drive Self-Test Options 189 Table 7o79.........GET DRIVE STATUS Subcommand Parameter List 190 Table 7o80.......................GET DRIVE STATUS Data Format 191 Table 7o81.............GET DRIVE STATUS Command Status Values 192 Table 7o82.......PASS DRIVE COMMAND Subcommand Parameter List 193 Table 7o83..............PASS DRIVE COMMAND Status Data Format 194 Table 7o84...........PASS DRIVE COMMAND Command Status Values 194 Table 7o85...PASS DRIVE COMMAND Standard Status Response Bits 195 Table 7o86..............READ HEADER Subcommand Parameter List 196 Table 7o87............................READ HEADER Data Format 196 Table 7o88................TRANSLATE Subcommand Parameter List 197 Table 7o89..............................TRANSLATE Data Format 197 Table 7o90................................START/STOP UNIT CDB 198 Table 7o91................................TEST UNIT READY CDB 200 Table 7o92.........................................VERIFY CDB 201 Table 7o93..........................................WRITE CDB 203 Table 7o94...............................WRITE (EXTENDED) CDB 205 Table 7o95...............................WRITE AND VERIFY CDB 207 Table 7o96...................................WRITE BUFFER CDB 210 Table 7o97......................Combined Header and Data Mode 211 Table 7o98.....................................WRITE LONG CDB 213 Table 7o99.................................WRITE LONG Command 214 Table Ao1......................................READ Algorithm 220 XT-8000S Product Specification & OEM Technical Manual TABLES Table Co1........................Defect Management Selections 226 Table Co2.....................Spares Versus Capacity, XT-8380 230 Table Co3.....................Spares Versus Capacity, XT-8760 231 Table Fo1.................................Buffer Ratio Values 240 Doc 1015586, Rev B xxvii Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 1 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 1.0 INTRODUCTION 1.1 GENERAL DESCRIPTION The XT-8000S# Family disk drives are low cost, high capacity, high performance, random access storage devices which use nonremovable 5.25 inch disks as storage media. Each disk surface employs one moveable head to access the data tracks. The total unformatted capacity of these disk drives ranges from 410 to 769 megabytes. The disk drive includes the Small Computer System Interface (SCSI) controller embedded in the disk drive electronics. Some of the resulting benefits of having an integrated controller include the elimination of a separate controller printed circuit board (PCB), reduction in the number of associated cables, and elimination of the controller-specific power supply. Low cost and high performance are achieved through the use of a rotary voice coil actuator and a closed loop servo system using a dedicated servo surface. The innovative MAXTORQ# rotary voice coil actuator provides performance usually achieved only with larger, higher powered linear actuators. The closed loop servo system and dedicated servo surface combine to allow state of the art recording densities (1,376 tracks per inch, and 31,596 bits per inch) in a 5.25 inch package. High capacity is achieved by a balanced combination of high areal recording density, run-length limited (RLL) data encoding, and high density packaging techniques. Maxtor's advanced MAXPAK# electronic packaging technique uses miniature surface mounted devices to allow all electronic circuitry to fit on one PCB. Advanced flexures and heads allow closer spacing of the disks; therefore, a greater number of disks fit in a 5.25 inch package. Maxtor's unique integrated disk drive motor/spindle design allows a deeper head/disk assembly (HDA) casting than conventional designs, thus permitting eight disks to be used. The disk drive's electrical interface is compatible with the American National Standards Institute (ANSI) SCSI standard X3.131-1986, plus the Common Command Set (CCS) requirements. Size and mounting conform to the industry standard 5.25 inch form factor for floppy and Winchester disk drives, and the same direct current (DC) voltages and connectors are used. XT-8000S Product Specification & OEM Technical Manual 1.2 KEY DISK DRIVE FEATURES FEATURE BENEFITS o Storage capacity of 410 Ideal for multiuser to 769 megabytes, systems and graphics unformatted workstations o Single PCB High reliability, ease of maintenance o Rotary voice coil and Fast, accurate head closed loop servo system positioning o Separate microprocessor- Fast access times, high controlled servo reliability, and high density packaging o Thin film metallic media Higher bit density and resolution and improved durability o Dedicated head landing High reliability, data and shipping zones with protected from mechanical automatic actuator lock shock o Brushless DC spindle Maximum storage capacity motor inside hub o Separate microprocessor- Precise speed control controlled spindle motor under all load conditions o Dynamic braking during Minimum head/disk contact power-down cycle time during spindown cycle o Industry standard DC No AC power required, ease power supply of integration requirements o Industry standard Ease of integration physical size and mounting 1.3 KEY CONTROLLER FEATURES FEATURE BENEFITS o Sophisticated, hardware- Minimum time on SCSI bus, based control of SCSI maximum bus use protocol Doc 1015586, Rev B 3 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual FEATURE BENEFITS o Up to 4.8 megabytes per Maximum SCSI bus use second data transfer rate in either asynchronous or synchronous mode o Synchronous offsets of Provides high performance up to 15 bytes on long cables o High performance buffer Simultaneous data manager transfers from disk to buffer, and from buffer to initiator o In-line sector sparing Maintains high performance over the life of the disk drive, even after numerous reassignments o Cylinder-oriented defect Maximizes formatted management capacity available to the system o Programmable cylinder No slipped revolutions skewing when crossing cylinder boundaries o Read-Ahead caching Maximizes throughput on sequential READ commands o 45,056 byte dual ported Maintains maximum SCSI bus first-in, first-out transfer rate (FIFO) buffer, nearly two tracks capacity o Hardware head switching No head skewing required to prevent slipped revolutions due to software overhead o Programmable Flexibility and more alternates/zones available capacity o Dedicated microprocessor SCSI bus unaffected by for SCSI disk drive interface functions such as SEEK o Error map on disk Automatic defect deallocation during format, no need for manual entry XT-8000S Product Specification & OEM Technical Manual FEATURE BENEFITS o ANSI SCSI Standard Compatibility and ease of X3.131-1986 Level 2 integration conformance o Full implementation of Availability of options CCS revision 4B and industry compatibility o Programmable 48-bit ECC High data integrity o Programmable automatic Flexibility and high data retry on READ errors integrity with automatic reallocation option o Interleave of 1:1 Maximum data throughput supported o Fully programmable Optimum SCSI bus disconnect/recon-nect performance capability o Sector sizes User flexibility and programmable from 256 to system compatibility 4,096 bytes o SCSI implementation Ease of integration and compatible with all upgrade Maxtor Winchester and optical disk drives o Differential interface Superior SCSI bus noise option immunity and longer transmission capability 1.4 SUMMARY OF SUPPORTED SCSI COMMANDS The commands supported by the disk drive are listed and discussed in Chapter 7.0, SCSI Command Descriptions. For more information on Group 0 and Group 1 commands for direct-access devices, see the reference documents below: o ANSI X3.131-1986, Small Computer System Interface (SCSI), American National Standards Institute, Inc., June 23, 1986. o X3T9.2/85-52 Rev 4.B Common Command Set (CCS), a document of the American Standards Committee. Doc 1015586, Rev B 5 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 6 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 2.0 SPECIFICATION SUMMARY 2.1 PERFORMANCE SPECIFICATIONS Table 2o1 Performance Specifications 2.2 FUNCTIONAL SPECIFICATIONS Table 2o2 Functional Specifications 2.3 ENVIRONMENTAL SPECIFICATIONS Table 2o3 Environmental Limits 2.4 PHYSICAL SPECIFICATIONS Table 2o4 Physical Dimensions 2.5 RELIABILITY SPECIFICATIONS Table 2o5 Reliability Specifications Doc 1015586, Rev B 7 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 2.6 ERROR RATES AT THE SCSI INTERFACE Table 2o6 Error Rates 2.7 DC POWER REQUIREMENTS Table 2o7 DC Power Requirements 2.8 STANDARDS AND REGULATIONS The Maxtor XT-8000S Family disk drives satisfy the following standards and regulations: UNDERWRITERS LABORATORIES (UL) = United States safety; UL 478, Standard for Safety, Electronic Processing Units and Systems. CANADIAN STANDARDS ASSOCIATION (CSA) = Canadian safety; CSA C22.2 No. 220, 1986, Information Processing and Business Equipment (Consumer and Commercial Products). VERBAND DEUTSCHER ELECTROTECHNIKER (VDE) = German safety; VDE 0806/8.81, Safety of Office Appliances and Business Equipment. INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC) = International safety commission; IEC 950 (formerly 380), Safety of Information Technology Equipment. FEDERAL COMMUNICATIONS COMMISSION (FCC) = United States radiation emissions; Part 15, Subpart J, Class B Consumer Computing Devices. CAUTION: Connections between equipment must be made with shielded cables, and a shielded power cord must be used to connect AC power to the unit. CAUTION: This equipment generates and uses radio frequency energy, and may cause interference to radio and television reception if not installed and used in strict accordance with the instructions in this manual. XT-8000S Product Specification & OEM Technical Manual The disk drive has been tested and found to comply with the limits for a Class B computing device, in accordance with the specifications in Subpart J of Part 15 of FCC Rules. These rules are designed to provide reasonable protection against radio and television reception interference in a residential installation. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference using one or more of the following measures: o reorient the receiving antenna o reorient the computer with respect to the receiver o move the computer away from the receiver o plug the computer into a different outlet, so that the computer and receiver are on different branch circuits If necessary, consult the dealer, or an experienced radio/television technician, for additional suggestions. You may find the FCC booklet How to Identify and Resolve Radio TV Interference Problems helpful. This booklet is available from the United States Government Printing Office, Washington, D.C., 20402, stock number 004-000- 00345-4. Maxtor is not responsible for any radio or television interference caused by unauthorized modifications to the disk drive. It is the responsibility of the user to correct such interference. Doc 1015586, Rev B 9 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 1 Maxtor Corporation Doc 1015586, Rev B 1 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 3.0 FUNCTIONAL CHARACTERISTICS 3.1 GENERAL THEORY OF OPERATION The disk drive consists of read/write, control, and interface electronics, read/write heads, a servo head, a head positioning actuator, a disk drive motor/spindle, the disk media, and an air filtration system. The components perform the following functions: o interpret and generate control signals o position the heads over the desired track o read and write data o provide automatic error correction to the data o provide a contamination-free environment o provide a controller to interact with the initiator o maintain precise spindle rotation speed 3.2 READ/WRITE CONTROL AND SCSI CONTROLLER ELECTRONICS All the disk drive and controller electronics are packaged on a single PCB. This PCB, which includes three microprocessors, performs the following disk drive functions: o data separation o reading and writing of data o index detection o head positioning o head selection o disk drive selection o fault detection o track zero detection o recalibration to track zero on power up o track position counter o power and speed control for the spindle disk drive motor o braking for the spindle disk drive motor o disk drive up-to-speed indication o reduced write current on the inner tracks o monitoring for WRITE FAULT conditions o control of all internal timing o generation of SEEK COMPLETE signals o RLL encoding/decoding The PCB also performs the following controller functions: o error detection and correction o SCSI bus disconnect/reconnect functions o SCSI bus arbitration o defect handling o data transfer Doc 1015586, Rev B 2 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual o automatic retries o data buffering o command linking o sector formatting 3.3 DISK DRIVE MECHANISM The HDA is a sealed subassembly containing the mechanical portion of the disk drive. A brushless DC drive motor contained within the spindle hub rotates the spindle and is controlled by a dedicated microprocessor. The motor and spindle are dynamically balanced to insure a low vibration level, and dynamic braking is used to quickly stop the spindle motor when power is removed. The HDA is shock mounted to minimize transmission of vibration through the frame. The frame is the mechanical assembly holding the HDA and PCB. 3.4 AIR FILTRATION SYSTEM The disks and read/write heads are assembled in a Class 100 environment and then sealed within the HDA. The HDA contains an absolute filter mounted inside the casting to provide constant internal air filtration (see Figure 3o1, Air Filtration System). A second absolute filter, located on the HDA top cover, permits pressure equalization between the internal and ambient air. Figure 3o1 Air Filtration System 3.5 HEAD POSITIONING MECHANISM The read/write heads are mounted on a head/arm assembly which is then mounted on a ball bearing supported shaft (see Figure 3o2, Head Positioning Mechanism). The voice coil, an integral part of the head/arm assembly, lies inside the magnet housing when installed in the disk drive. Current from the power amplifier, which is controlled by the servo system, induces a magnetic field in the voice coil. This electrically induced field either aids or opposes the existing fields of the permanent magnets. The interaction of the permanent and induced magnetic fields causes the voice coil to move. Since the head/arm assemblies are mounted on the voice coil, the voice coil movement is translated through the shaft pivot point directly to the heads. The movement of the head/arm Doc 1015586, Rev B 3 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual assembly in conjunction with the information from the servo system positions the heads over the correct cylinder. Figure 3o2 Head Positioning Mechanism Movement of the voice coil actuator is controlled by the servo feedback signal from the servo head. The servo information is written onto the disk at the factory and provides the following control signals for the actuator: track-crossing signals during a seek operation, track- following signals during on cylinder operation, and timing information such as index and servo clock. Servo information also provides the timing necessary to divide a track into the sectors used for data storage. The servo control system has a dedicated microprocessor for fast, optimized performance. 3.6 READ/WRITE HEADS AND DISKS The disk drive employs state of the art sliders and flexures. The configuration of the sliders and flexures provides improved aerodynamic stability, superior head/disk compliance and an extremely high signal-to-noise ratio. The disk media is a thin, nickel-cobalt, metallic film deposited on 130 millimeter diameter aluminum substrates. The coating formulation together with the low load- force/low mass heads permits highly reliable contact start/stop operation. The nickel-cobalt metallic film yields high amplitude signals, and very high resolution performance compared to conventional oxide coated media. The metallic media also provides a highly abrasion and impact resistant surface, decreasing the potential for damage caused by shipping shock and vibration. Data on each of the data surfaces is read by one read/write head, and each head can access 1,632 physical tracks. There is one surface dedicated to servo information in each disk drive. 3.7 TRACK AND SECTOR FORMAT The standard track format is organized into sectors (see Figure 3o3, Track Format). The sectors are addressed via Doc 1015586, Rev B 4 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual the logical block address (LBA) in the SCSI commands. The method of encoding used is 2, 7 RLL. Figure 3o3 Track Format The data field indicated in Figure 3o3 is 512 bytes. The number of sectors per track for different data fields is summarized in Table 3o1, Data Field Size vs. Sectors per Track. Table 3o1 Data Field Size vs. Sectors per Track 3.8 SCSI INTERFACE 3.8.1 Initiator-Target Configurations The SCSI initiator interface offers a number of unique advantages which facilitate the interconnection of the disk drive with one (or more) computer systems. Unlike traditional microcomputer disk interfaces, such as ST506, SCSI supports multiple peripherals and different peripheral types all operating on the same bus structure. Figure 3o4, Typical SCSI Configurations, shows examples of typical configurations. Figure 3o4 Typical SCSI Configurations The disk drive also supports multiple host configurations consistent with the established arbitration cycle outlined in the SCSI standards. Configuration changes are made by changing the SCSI address jumpers. These jumpers should be set and verified when the disk drive is installed in the system (jumper settings are covered in Chapter 4, User Selectable Options). Doc 1015586, Rev B 5 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual The SCSI implementation used on the disk drive is intended to facilitate high-speed data transfer between the initiator and the disk drive. Interconnection between the initiator(s) and the disk drive is via a fifty-conductor ribbon cable and uses the single-ended alternative (the single-ended alternative allows up to 6 meters of cable length). 3.8.2 Logical/Electrical Signal Definitions The SCSI bus uses +5 volts (termination power), ground, and eighteen signal lines. Nine signals are for the 8-bit data bus with one data parity bit; the other nine signals are the SCSI control lines which coordinate access to the bus for transfers of commands, data, status, and messages. The interface signals are listed below; please refer to the published SCSI standard for further details. Pin assignments of the connector are provided in sections 3.8.3 Pin Assignments and Connector (Single Ended) and 3.8.4 Pin Assignments and Connector (Differential) later in this chapter. Across the SCSI bus all initiator signals are low-true for the single ended version. The signals are asserted, or active, at 0 to 0.5 volts DC, and deasserted, or inactive, at 2.5 to 5.25 volts DC. This low-true logic is indicated by the negative sign which precedes the signal name. -RST The -RST (reset) signal is an OR-tied signal asserted by the initiator, causing the drive to do a "hard" RESET, self configure and return to the IDLE condition. This signal is normally used during a power-up sequence. The - RST pulse should be at least 25 microseconds wide. -SEL The -SEL (select) signal, accompanied by the disk drive's SCSI ID bit (zero through seven), is asserted by the initiator and causes the disk drive to be selected. The - SEL line must be negated by the initiator after the disk drive asserts the -BSY line in response to a proper selection. The signal can be asserted by the arbiter (initiator or drive) in the ARBITRATION phase. The signal is also asserted by the disk drive during the RESELECTION phase. -BSY The -BSY (busy) signal is an OR-tied signal asserted by the drive, indicating that the bus is being used. It is also asserted by the arbiter during the ARBITRATION phase and by the initiator and the disk drive during the RESELECTION phase. Doc 1015586, Rev B 6 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual -C/D Assertion of the -C/D (control/data) signal by the disk drive indicates that command, status, or message information is to be transferred on the data bus. Negation of this line indicates that data is to be transferred on the data bus. -I/O When the -I/O (input/output) signal is asserted by the disk drive it indicates that information is transferred to the initiator from the disk drive. Negation of the signal indicates that information is transferred to the disk drive from the initiator. Note that IN means toward the initiator. -REQ When asserted by the disk drive, the -REQ (request) signal indicates that a byte is to be transferred on the data bus. -REQ is negated following assertion of the -ACK line by the initiator. -ACK The -ACK (acknowledge) signal is asserted by the initiator, following the assertion of the -REQ line, to indicate that data has been accepted by the initiator, or that data is ready to be transferred from the initiator to the disk drive. -ACK is negated following negation of the -REQ line. -ATN The -ATN (attention) signal is asserted by the initiator to indicate the ATTENTION condition, which is a request by the initiator for the disk drive to enter the MESSAGE OUT phase. -MSG The -MSG (message) signal is asserted by the disk drive during one of the message phases. Messages may be either IN or OUT, depending on the state of the -I/O signal. -DB (7-0, P) The eight bidirectional data bus lines (DB 7-0) and the parity line (DBP) are used to transfer 8-bit parallel data to or from the initiator. Bit seven is the most significant bit. Bits zero through seven are also used as SCSI ID bits during the ARBITRATION, SELECTION and RESELECTION phases. Data bus parity (DBP) is odd. 3.8.3 Pin Assignments and Connector (Single Ended) The disk drive communicates with an initiator system via a fifty-pin connector, J1. The logical/electrical configuration of the SCSI connector is given in Table 3o2, Doc 1015586, Rev B 7 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual Connector Pin Assignments (Single Ended). Note that the minus sign (-) indicates low-true logic, and that all odd- numbered pins are return (ground) pins for the associated even-numbered pins, except for pin twenty-five, which is not connected. Pin one is located on the end of J1 closest to the DC power connector, J3. (See Figure 3o5, Connector Locations, Rear View of Drive.) Table 3o2 Connector Pin Assignments (Single Ended) 3.8.4 Pin Assignments and Connector (Differential) The disk drive communicates with an initiator system via a fifty-pin connector, J1. The logical/electrical configuration of the SCSI connector is given in Table 3o3, Connector Pin Assignments (Differential). All signals consist of two lines denoted +SIGNAL and -SIGNAL. A signal is true when +SIGNAL is more positive than -SIGNAL. A signal is false when -SIGNAL is more positive than +SIGNAL. All assigned signals shall be terminated at each end of the cable with a terminator network. Resistor tolerances in the terminator network shall be ~5% or less. The DIFFSENS signal of the connector is used as an active high enable for the differential drivers. If a single- ended device or terminator is inadvertently connected, this signal is grounded, disabling the differential drivers. See Table 3o3, Connector Pin Assignments (Differential). Table 3o3 Connector Pin Assignments (Differential) Figure 3o5 Connector Locations, Rear View of Drive Connection to J1 is via a nonshielded fifty-conductor connector, consisting of two rows of twenty-five female contacts on 0.1 inch centers. Figure 3o6, SCSI Cable Doc 1015586, Rev B 8 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual Connector, shows the configuration and dimensions of a suitable mating connector. Recommended strain-relief connectors are AMP part number 1-499506-2, or Dupont part number 669002 (66900-250). Use of a keyed connector is recommended. Figure 3o6 SCSI Cable Connector 3.9 ELECTRICAL POWER INTERFACE This subsection describes the power-up sequence for the disk drive, and the two connectors associated with the electrical power interface. These connectors are the power connector, J3, and the frame ground connector, J4. Doc 1015586, Rev B 9 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 3.9.1 Power-Up Sequence DC power (+5 volts and +12 volts) may be supplied in any order. Both power supplies must be present, and within the tolerances of the power sensing circuit, before the motor will spin up. Typical current draw during power up is shown in Figure 3o7, Motor Start Current Requirements. When the spindle reaches full speed, the actuator lock automatically disengages. The disk drive performs automatic seek calibration during start up for optimum seek performance. The disk drive spins up and becomes ready in 20 to 30 seconds. The disk drive executes its recalibration sequence whenever power is applied or the START STOP UNIT command is received. You may delay starting the spindle motor, to minimize power surges in multidrive configurations, by using the jumper options (see 4.2 Drive Power-Up Options later in this manual). The two jumpers controlling the disk drive power-up options are also covered in this section. Figure 3o7 Motor Start Current Requirements 3.9.2 Power Connector The DC power connector, J3 (shown in Figure 3o8, J3 Connector), is a four-pin AMP MATE-N-LOCK connector, part number 3505430-1. The recommended mating connector is AMP part number 1-480424-0, using AMP pins part number 350078- 4 (strip) or part number 61173-4 (loose piece). J3 pins are numbered and assigned as shown in Figure 3o8. Figure 3o5, Connector Locations, Rear View of Drive, shows the location of J3 on the disk drive. Figure 3o8 J3 Connector 3.9.3 Frame (HDA) Ground Connector The ground connector, J4, is a Faston-type connection, AMP part number 61761-2. The recommended mating connector is AMP part number 62187-1. (See Figure 3o5.) If wire is used, the hole in J4 accommodates a wire size of 18 gauge wire, maximum. This connection is on the rear of the HDA, Doc 1015586, Rev B 10 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual accessible through an opening in the frame of the disk drive. Figure 3o5, Connector Locations, Rear View of Drive, shows the location of J4 on the disk drive. 3.10 MOUNTING AND INSTALLATION The disk drive may be mounted in any orientation. However, in any final mounting configuration, ensure that the operation of the three shock mounts is not restricted (these mounts isolate the HDA from the frame). Also, certain switching power supplies may emanate electrical noise which degrades the specified read error rate; therefore, it is suggested that the disk drive be oriented so that the PCB assembly is not adjacent to these noise sources. Eight mounting holes, four on the bottom and two on each side, are provided for mounting the disk drive into an enclosure. The size and location of these holes, shown in Figure 3o9, Mechanical Outline, Top and Side Views, are identical to industry standards. Overall height, width, and depth, along with other key dimensions, are shown in Figure 3o9, and Figure 3o10, Mechanical Outline, Isometric View. Figure 3o9 Mechanical Outline, Top and Side Views Figure 3o10 Mechanical Outline, Isometric View The faceplate may be removed in installations that require it. Remove the two C-clips and unplug the light-emitting diode (LED) cable from the PCB, as shown in Figure 3o11, Removable Faceplate. Figure 3o11 Removable Faceplate Doc 1015586, Rev B 11 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 3.11 SHIPPING At power down, the heads are automatically positioned over the nondata, dedicated landing zone on each disk surface. The automatic shipping lock solenoid is also engaged at this time. Maxtor ships the disk drive in single- and multipack shipping containers. Users can ship the disk drive installed when the nonoperating shock and vibration limits are not exceeded. Doc 1015586, Rev B 12 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 31 Maxtor Corporation Doc 1015586, Rev B 31 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 4.0 USER SELECTABLE OPTIONS Jumper locations are identified in Figures 4o1 and 4o2, PCB Layout (single ended version and differential version). Figure 4o1 PCB Layout (Single Ended Version) Figure 4o2 PCB Layout (Differential) 4.1 SCSI ID SELECTION SCSI ID jumpers (JP35 through JP37) are provided to configure each disk drive with a SCSI device ID for use in multiple SCSI device configurations. Table 4o1, SCSI ID Jumpers, is a reference table for the SCSI ID jumper configuration, the ID, and the priority on the SCSI bus. An ID of seven is the highest priority in a multiple device configuration, and is usually used for the initiator. Table 4o1 SCSI ID Jumpers The disk drive is shipped from the factory with a SCSI ID of six. This assures that sufficient jumpers are available for any address except seven, which is usually reserved for the host system. The SCSI ID can also be set remotely through the auxiliary connector (see 4.9 Auxiliary Connector later in this chapter). The SCSI ID jumpers must be removed to use the auxiliary connector option, and any shorting required for a selected SCSI ID is done outside the disk drive. Doc 1015586, Rev B 32 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 4.2 DRIVE POWER-UP OPTIONS In order to allow for system power supply constraints, which may require minimizing surge current when powering up multiple disk drives, three modes of start- up sequencing are provided (see Table 4o2, Summary of Power-Up Options). Table 4o2 Summary of Power-Up Options Start by ID Sequence: Both JP14 and JP38 are out. The disk drive delays spinup for approximately 11 to 13 seconds multiplied by the SCSI ID. This allows for power-up sequencing. A RESET condition results in the disk drive delaying its spinup according to its SCSI ID. Wait for START Command: JP14 is out and JP38 is in. The disk drive does not spinup until the initiator issues a START STOP UNIT command with the start bit equal to one. Start When Power Is Applied: JP14 is in and JP38 is out. The motor starts as soon as power is applied. The disk drive is shipped in this configuration. 4.3 TERMINATOR POWER SELECTION Single Ended Version: Power to the terminators may come internally from the disk drive, or externally from the SCSI bus. If JP41 is in, the terminator power is provided by the disk drive. If JP34 is in, the terminator power is external, from the SCSI bus. If both JP41 and JP34 are in, terminator power is provided from the disk drive and to the SCSI bus. Hence, the disk drive is at one end of the SCSI bus with terminators in place and is also supplying terminator power for the device at the other end of the SCSI bus (see Figure 3o4, Typical SCSI Configurations). Additional discussion of the termination of the SCSI bus and location of the disk drive on the bus is presented in 4.8 Interface Termination later in this chapter. Doc 1015586, Rev B 33 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual Differential Version: The differential version does not provide for termination on the PCB. Therefore, JP34 is shipped installed and JP41 is not supported. This will provide +5v to the SCSI bus for external termination. 4.4 WRITE PROTECT OPTION The write protect jumper, JP18, is used to protect the data written on the disk drive. When the jumper is in data cannot be written onto the disk drive; only read operations can be executed. Installation of JP18 also grounds the remote write protect line, J2, pin seven, and prevents remote control of write protect through J2, pin seven, on the ten-pin connector. As shipped from the factory JP18 is out, allowing normal reading and writing, or optional remote control through connector J2. See 4.9 Auxiliary Connector later in this chapter, for details of the J2 connector. 4.5 PARITY OPTION The parity jumper, JP40, enables (in) or disables (out) odd parity detection in the disk drive. Odd parity is always generated by the disk drive and provided to the SCSI bus. The disk drive is shipped with JP40 in, enabling parity detection. 4.6 OTHER JUMPERS The other jumper positions shown are not user selectable. These jumpers are for factory use only. The user should avoid changing these jumpers or improper operation may occur. 4.7 SECTOR SIZE The disk drive is shipped from the factory formatted with 512-byte sectors. Configuration parameters are default values in all optional cases. It is recommended that users reformat the disk drive with the user's sector size, using the P list, and the user's configuration parameters. Doc 1015586, Rev B 34 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 4.8 INTERFACE TERMINATION SCSI devices require proper interface termination. The first device and the last device on a SCSI bus daisy chain must be terminated (see Figure 3o4, Typical SCSI Configurations). Remove the terminators from any devices in between. For instance, if a disk drive is in the middle of a SCSI bus daisy chain, remove its terminators. The disk drive terminators are shown in Figures 4o1 and 4o2, PCB Layout. Terminator pin one is marked with a dot on the terminator as shown in Figures 4o1 and 4o2, PCB Layout. The terminators (RN17, RN18, and RN19) all look like the side view inset in the figure. The orientation of the terminator on the PCB is also shown. Note that the PCB's hole/solder pad for pin one has a square outline, whereas all the other holes/pads have a round outline. Also, note that pin one is always the closest pin to the power connector, J3. NOTE: All terminator packs (RN17 through RN19) must be oriented with the dot towards J3 for the disk drive to work properly. As shipped, the interface signal lines are terminated with three removable 220/330 ohm resistor network packs. The devices driving the disk drive inputs should be open collector devices capable of sinking at least 48 milliamps at a voltage level of less than 0.5 volts DC (7438 or equivalent). Devices receiving the disk drive outputs should be of SCHMITT trigger type to improve noise immunity (74LS14, 74LS240, or equivalent). The initiator should not load the bus with more than one standard low power Schotky transistor-transistor logic (LSTTL) input load per line, and should terminate all signals with 220/330 ohm terminators. NOTE: The differential version does not provide for termination on the PCB. External terminators are available from Maxtor. 4.9 AUXILIARY CONNECTOR Connector J2 in Figure 3o5, Connector Locations, Rear View of Drive, is an auxiliary connector providing remote control of the write protect feature and the Doc 1015586, Rev B 35 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual SCSI ID, and the ability to carry the LED signal beyond the disk drive. The auxiliary connector is a Berg 68451-121, ten-pin part. The mating connector is a 3M 3473-6010 part. Pin assignments are as in Table 4o3, Auxiliary Connector Pin Assignments (also see Figure 3o5, Connector Locations, Rear View of Drive). Table 4o3 Auxiliary Connector Pin Assignments When pin seven is connected to ground, the disk drive is protected from writing, regardless of commands sent to the disk drive via the SCSI interface. The write protect terminal may also be connected to the cathode (negative lead) of an LED. This LED should have its anode (positive lead) connected to a positive voltage source. When the disk drive enters the write protect mode, the write protect signal becomes true (low) and the LED lights. For remote write protect, JP18 must be removed (see 4.4 Write Protect Option earlier in this chapter). When an LED is connected to pin one (+) and pin five (- ), that LED functions in the same manner as the LED which is mounted on the disk drive's faceplate. This is typically used in cases where the disk drive is mounted in a position where the disk drive's LED is not visible and the faceplate is removed. Pin three is not present so that users can key the mating connector. Pin three of the mating connector should be blocked for this purpose. The SCSI ID of the disk drive may be programmed remotely by selectively connecting pins six, eight, and ten to ground, or leaving them open. The various combinations are shown in Table 4o4, Remote SCSI ID Programming Combinations. Table 4o4 Remote SCSI ID Programming Combinations Doc 1015586, Rev B 36 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual SCSI ID jumpers (JP35 through JP37) must be removed for the remote SCSI ID option. 4.10 SPINDLE SYNCHRONIZATION CONTROL Spindle synchronization is a feature that allows up to forty-eight disk drives to synchronize the rotational position of their spindles. Pin assignments for connector J6 are shown in Table 4o5, J6 Pin Assignments. For additional information on spindle synchronization, call Maxtor at (408) 432-1700 and ask for the Marketing department. Table 4o5 J6 Pin Assignments Doc 1015586, Rev B 37 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 38 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 5.0 LOGICAL CHARACTERISTICS The following information is based on the ANSI SCSI standard (X3.131-1986), and the Common Command Set (CCS). For more information, refer to these publications. 5.1 POWER UP AND BUS RESET The following sections describe the sequence of events during drive self-test and initialization sequences. The self-test sequence occurs before the initialization sequence. 5.1.1 Self-Test Sequence The self-test sequence is executed upon drive power up. The self-test sequence verifies the integrity of the hardware. This test is not an exhaustive hardware diagnostic, but checks the major components for full function. The drive does not respond to SELECTION for the first 250 milliseconds of the self-test. After 250 milliseconds have elapsed, the drive responds to SELECTION with a BUSY status for 2 to 3 seconds: this time is spent completing the remaining self-test sequences, initializing the SCSI circuitry, and enabling the SCSI interrupts. After the self-test is complete and the interface circuitry is initialized (approximately 3 seconds), the drive responds to SELECTION with CHECK CONDITION status and the appropriate sense data (i.e., UNIT ATTENTION, POWER ON/RESET condition). The self-test sequence consists of the following events: o Hardware Reset Test - This routine tests the microprocessor, buffer controller, disk formatter, and SCSI reset latch for the proper power up condition. If any of these tests fail, the drive can only be reset by a POWER UP condition. o Microprocessor Test - This routine tests the microprocessor's internal memory, timers, and register bank switching for proper operation. o Erasable Programmable Read Only Memory (EPROM) Checksum Test - This routine performs a checksum calculation on the controller firmware EPROM and compares it against the checksum stored in the EPROM. o Buffer Controller Test - This routine tests the buffer controller for proper operation. All the registers are tested and the chip is engaged to access random-access memory (RAM). Doc 1015586, Rev B 39 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual o Dynamic RAM Test - This routine tests the dynamic RAM by writing and reading different patterns to memory. In addition, the buffer controller is tested for proper refresh operation and parity detection. This test also tests the memory parity interrupt. o Disk Formatter Test - This routine tests the disk formatter chip by writing and reading all possible patterns to each of the disk formatter chip registers. After the registers are tested, the interrupts are tested to ensure that the formatter chip generates an interrupt when a command completes. o SCSI Controller Test - This routine tests the SCSI controller chip by executing the chip diagnostic command. After the diagnostic test completes, the interrupts are tested to ensure that the SCSI chip generates an interrupt when a command completes. Finally, the registers are tested by writing and reading all possible patterns to each of the SCSI controller chip registers. If any portion of the self-test fails, except the hardware reset test, the drive can be reset by a SCSI bus RESET condition or a power up RESET condition. The failure of the hardware reset test is considered a catastrophic failure and the controller can only be reset from such a failure by a power up RESET condition. 5.1.2 Initialization Sequence The initialization sequence is executed for any one of the following three reasons: o a POWER UP condition occurs o the SCSI bus -RST signal is asserted o a BUS DEVICE RESET message (on the SCSI bus) is received After a successful initialization, the first command from each initiator is terminated with CHECK CONDITION status. The sense data is set to UNIT ATTENTION/POWER ON, RESET, or BUS DEVICE RESET OCCURRED. Until the drive has spun up, any command sent by an initiator which requires a ready drive for GOOD completion status, is terminated with CHECK CONDITION status. The sense data is set to DRIVE NOT READY. Commands that may complete with GOOD status prior to the drive being ready are REQUEST SENSE, INQUIRY, RESERVE UNIT, RELEASE UNIT, START STOP UNIT, READ BUFFER, and WRITE BUFFER. XT-8000S Product Specification & OEM Technical Manual Note that the INQUIRY command results in the general model designation (XT-8000S) being returned prior to the drive being READY. Afterwards, the specific model number is returned. After a RESET CONDITION occurs, the first command sent by the initiator that causes a medium access loads the saved mode parameters into the current mode parameters. 5.1.3 Self Configuration When the drive powers up or a RESET CONDITION occurs, it configures itself from the parameters and information saved on the medium from the previous format operation. This includes the model number returned in the INQUIRY command and the mode parameters. Refer to 7.4 MODE SELECT, and 7.5 MODE SENSE later in this manual, which describe the mode parameters. 5.1.4 UNIT ATTENTION Condition A UNIT ATTENTION condition is generated for each initiator whenever the drive has been reset (by a BUS DEVICE RESET message or a RESET condition), or when the mode parameters have been changed by other initiators. The UNIT ATTENTION condition persists for each initiator until that initiator issues any command other than INQUIRY. The generation of a UNIT ATTENTION condition supercedes any pending sense data. If an INQUIRY command is received from an initiator with a pending UNIT ATTENTION condition, the last UNIT ATTENTION generated condition is reported. The drive returns the INQUIRY data and does not clear the UNIT ATTENTION condition. 5.2 BUFFERING SCHEME The drive has 64 kilobytes of RAM. The drive uses 4 kilobytes of RAM for a scratchpad, 16 kilobytes of RAM for a write buffer and 45,056 bytes of RAM for a data buffer. The drive will use the data buffer for read-ahead cache if this feature is enabled. The drive will use the data buffer for write operations if the transfer length exceeds 16 kilobytes. Normally, the drive uses the split buffering, that is, separate buffers for write operations (write buffer) and read operations (data buffer) to optimize throughput. Doc 1015586, Rev B 41 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual This is particularly advantageous in systems that perform extensive read-modify-write processes. The buffer controller is dual parted, allowing simultaneous transfers to and from the initiator and the medium. XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 1 Maxtor Corporation Doc 1015586, Rev B 1 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.0 SCSI PHASES AND MESSAGES The condition on the SCSI bus can be divided into eight distinct phases: BUS FREE phase ARBITRATION phase SELECTION phase RESELECTION phase COMMAND phase \ DATA phase \ These phases are collectively termed the STATUS phase / Information Transfer phases. MESSAGE phase / The various phases are defined by the state of the SCSI bus signals -SEL, -BSY, -MSG, -C/D, -I/O, -REQ, and -ACK (see Table 6o1, Signal States and Bus Phases). The SCSI bus can never be in more than one phase at a time. Figure 6o1, Signal Sequence Chart for SCSI Phases, shows the signal sequence of the eight phases. See the figure while reading the following sections. NOTE: The condition of the control lines for information transfer is valid only when the SCSI bus -REQ signal is asserted; therefore, the disk drive is not "in a phase" unless the --REQ signal is asserted. Table 6o1 Signal States and Bus Phases Figure 6o1 Signal Sequence Chart for SCSI Phases 6.1 BUS FREE PHASE The BUS FREE phase is used to indicate that no SCSI device is actively using the SCSI bus, and that it is available for subsequent users. The BUS FREE phase occurs when the drive releases -BSY following a RESET condition or certain message phases (i.e., COMMAND COMPLETE and DISCONNECT). Doc 1015586, Rev B 2 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.2 ARBITRATION PHASE The ARBITRATION phase allows one SCSI device to gain control of the SCSI bus so that it can assume the role of an initiator or target (drive). The arbitrating device waits for the BUS FREE phase to occur. It then asserts its own SCSI ID bit and -BSY. The arbitrating device then examines the data bus. If a higher priority SCSI ID bit exists on the data bus, the arbitrating device loses arbitration and releases -BSY and the data bus. Otherwise, the arbitrating device wins arbitration and asserts -SEL. NOTE: Implementation of the ARBITRATION phase is a system option. Systems that do not implement this option can have only one initiator. The ARBITRATION phase is required for systems that use the disconnect/reconnect feature. 6.3 SELECTION PHASE If the initiator wins arbitration, it enters the SELECTION phase by continuing to assert its own initiator SCSI ID bit and asserting the drive's SCSI ID bit. The initiator then negates -BSY (-SEL remains asserted by the initiator). If the initiator expects the drive to disconnect/reconnect, the initiator must assert the -ATN line prior to the negation of -BSY. If the initiator does not support arbitration, then the SELECTION phase is entered from the BUS FREE phase. The initiator asserts only the disk drive's SCSI ID bit and asserts -SEL. During the SELECTION phase, the drive maintains a negated -I/O line so that the SELECTION phase may be distinguished from the RESELECTION phase. The drive determines that it has been selected by detecting its SCSI ID bit asserted on the bus (as determined by the ID jumpers, see 4.1 SCSI ID Selection earlier in this manual). If more than two IDs are asserted on the data bus, or parity is enabled and bad parity is detected, the drive does not respond to the SELECTION phase. The drive asserts -BSY after detecting that it has been selected. At this point, the initiator must negate -SEL and may remove the IDs from the data bus. Doc 1015586, Rev B 3 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.4 RESELECTION PHASE After disconnecting to free the bus for other activity, the drive reconnects when it is ready to transfer data or status across the bus. The drive arbitrates for the bus and, if it wins, reselects the initiator. The RESELECTION phase is similar to the SELECTION phase, except that the - I/O signal line is asserted. The drive asserts its own SCSI ID bit and the SCSI ID bit of the initiator which is being reselected. The drive releases -BSY (-BSY was already asserted during arbitration) and continues to assert -SEL. The initiator detects that it has been selected and responds by asserting -BSY. The drive detects that the -BSY signal is now true and responds by also asserting -BSY (at this point, both the initiator and the drive are holding the -BSY signal low). The drive then releases -SEL and the initiator responds by releasing -BSY (-BSY is still being asserted by the drive). See Figure 6o1, Signal Sequence Chart for SCSI Phases. After reselecting the initiator, the drive sends an IDENTIFY message to identify itself to the initiator. If the initiator does not respond to the reselection within a selection time-out delay (see Table 6o2, SCSI Bus Timing), the drive releases the bus and then rearbitrates for the bus, trying to reselect the initiator. It does this up to 255 times, or until the initiator responds or the drive is reset. NOTE: The drive does not disconnect if, during the SELECTION phase, the initiator does not set its initiator SCSI device ID on the bus and if the initiator does not send an IDENTIFY message out (with bit six asserted) to the drive. Table 6o2 SCSI Bus Timing 6.5 INFORMATION TRANSFER PHASES The -C/D, -I/O, and -MSG signals are used to distinguish between the different information transfer phases (COMMAND, DATA, STATUS, and MESSAGE). The drive controls these three signals, and, therefore, controls all changes from one phase to another. The initiator can request a MESSAGE OUT phase by asserting -ATN, and the drive can cause a BUS FREE phase by negating/releasing -SEL and -BSY (and all other SCSI bus signals). Doc 1015586, Rev B 4 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual The information transfer phases use one or more -REQ/-ACK handshakes to control the information transfer. Each - REQ/-ACK handshake allows the transfer of one byte of information. During the information transfer phases, -BSY remains true and -SEL remains false. Additionally, during the information transfer phases, the drive continuously envelopes the -REQ/-ACK handshake(s) with -C/D, -I/O, and -MSG in such a manner that these control signals are valid for a bus settle delay (see Table 6o2, SCSI Bus Timing) before the assertion of -REQ of the first handshake, and remain valid until the negation of -ACK at the end of the last handshake. 6.5.1 Asynchronous Information Transfer The drive controls the direction of information transfer by means of the -I/O signal. When -I/O is true, information is transferred from the drive to the initiator. When -I/O is false, information is transferred from the initiator to the drive. If -I/O is true (transfer to the initiator), the drive first asserts -DB (7-0, P) to their desired values, delays at least one deskew delay, plus a cable skew delay (see Table 6o2, SCSI Bus Timing), and then asserts -REQ. -DB (7-0, P) remain valid until -ACK is true at the drive. The initiator reads -DB (7-0, P) after -REQ is true, then signals its acceptance of the data by asserting -ACK. When -ACK becomes true at the drive, the drive may change or release -DB (7-0, P), and negates -REQ. After -REQ is false, the initiator then negates -ACK. After -ACK is false, the drive may continue the transfer by asserting - DB (7-0, P) and -REQ as described above. If -I/O is false (transfer to the drive), the drive requests information by asserting -REQ. The initiator drives -DB (7-0, P) to their desired values, delays at least one deskew delay, plus a cable skew delay (see Table 6o2, SCSI Bus Timing), and asserts -ACK. The initiator continues to drive -DB (7-0, P) until -REQ is false. When -ACK becomes true at the drive, the drive reads -DB (7-0, P) and then negates -REQ. When -REQ becomes false at the initiator, the initiator may change or release -DB (7-0, P), and negates -ACK. The drive may continue the transfer by asserting -REQ as described above. 6.5.2 Synchronous Data Transfer Synchronous data transfer is optional, and may be used only if previously agreed to by the initiator and drive through the message system (see 6.6.16 SYNCHRONOUS DATA TRANSFER REQUEST Message later in this chapter). The Doc 1015586, Rev B 5 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual messages determine the use of synchronous mode by the initiator and the drive, and establish a -REQ/-ACK offset and a transfer period. The synchronous mode, once established, remains in effect for all DATA phases until a RESET condition or power cycle occurs, or until one of the devices elects to modify the agreement. The -REQ/-ACK offset specifies the maximum number of -REQ pulses that can be sent by the target in advance of the number of -ACK pulses received from the initiator, thereby establishing a pacing mechanism. If the number of -REQ pulses exceeds the number of -ACK pulses by the -REQ/-ACK offset, the drive does not assert -REQ until the next -ACK pulse is received. A requirement for successful completion of the DATA phase is that the number of -ACK and -REQ pulses be equal. The transfer period specifies the minimum time allowed between leading edges of successive -REQ and -ACK pulses. The drive asserts the -REQ signal for a minimum of one assertion period. The drive waits at least the greater of a transfer period from the last transition of -REQ to true, or the minimum of a negation period from the last transition of -REQ to false before the disk drive asserts the -REQ signal. The initiator sends one pulse of the -ACK signal for each -REQ pulse received. The initiator asserts the -ACK signal for a minimum of one assertion period. The initiator waits at least the greater of a transfer period from the last transition of -ACK to true, or for a minimum of a negation period from the last transition of -ACK to false, before the initiator asserts the -ACK signal. If -I/O is true (transfer to the initiator), the drive first asserts -DB (7-0, P) to their desired values, waits at least one deskew delay, plus one cable skew delay (see Table 6o2, SCSI Bus Timing), and then asserts -REQ. -DB (7+0, P) are held valid for a minimum of one deskew delay, plus one cable skew delay, plus one hold time (see Table 6o2) after the assertion of -REQ. The drive asserts -REQ for a minimum of one assertion period. The drive may then negate -REQ and change or release -DB (7-0, P). The initiator reads the value on -DB (7-0, P) within one hold time of the transition of -REQ to true. The initiator then responds with a -ACK pulse. If -I/O is false (transfer to the drive), the initiator transfers 1 byte for each -REQ pulse received. After receiving a -REQ pulse, the initiator first asserts -DB (7-0, P) to the desired value, delays at least one deskew delay, plus one cable skew delay (see Table 6o2, SCSI Bus Doc 1015586, Rev B 6 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual Timing), and then asserts -ACK. The initiator holds -DB (7-0, P) valid for at least one deskew delay, plus one cable skew delay, plus one hold time (see Table 6o2) after the assertion of -ACK. The initiator asserts -ACK for a minimum of one assertion period. The initiator may then negate -ACK and may change or release -DB (7-0, P). The drive reads the value of -DB (7-0, P) within one hold time of the transition of -ACK to true. 6.5.3 COMMAND Phase After being selected and processing the IDENTIFY message, if any, the drive normally switches to the COMMAND phase. The 6 or 10 bytes of command information (command descriptor block, or CDB) are transferred from the initiator to the drive. If enabled, parity is checked on each command byte. If bad parity is detected, the command is aborted. The drive switches to the STATUS phase, returns CHECK CONDITION status, and sets the sense data to ABORTED COMMAND/PARITY ERROR for that initiator. The drive then switches to the MESSAGE phase, returns a COMMAND COMPLETE message, and goes to the BUS FREE phase. After each command byte transfer, the -ATN bit is checked; if the -ATN line is active the drive switches to the MESSAGE OUT phase and receives and then acts on the message. 6.5.4 DATA IN and DATA OUT Phases In commands that require a DATA phase (READ, WRITE, MODE SELECT, etc.), the drive enters a DATA phase. During the DATA IN phase, data is transferred from the drive to the initiator. During the DATA OUT phase, data is transferred from the initiator to the drive. If bus parity is enabled and bad parity is detected, the command is aborted. The controller switches to the STATUS phase, returns CHECK CONDITION status, and sets the sense data to ABORTED COMMAND/PARITY ERROR for that initiator. The drive then switches to the MESSAGE phase, returns a COMMAND COMPLETE message, and goes to the BUS FREE phase. After each block, or group of blocks, is transferred, the -ATN bit is checked; if set, the disk drive switches to the MESSAGE phase to receive, and then act on, the message. Doc 1015586, Rev B 7 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.5.5 STATUS Phase After completing any command (successfully or unsuccessfully, as indicated by the status byte), the drive switches to the STATUS phase and returns the status byte to the initiator. The drive also switches to the STATUS phase for reporting a BUSY, INTERMEDIATE-GOOD, or RESERVATION CONFLICT status. The drive does not go to the STATUS phase if it is cleared by a BUS DEVICE RESET or ABORT message, or by a "hard" RESET condition. Following the STATUS phase, the drive enters the MESSAGE phase. The format of the status byte containing the command completion information is defined in Table 6o3, Status Byte. Table 6o3 Status Byte The reserved bits are set aside for future standardization and is always set to zero. The status code field is used to specify the status of the completed command. Table 6o4, Status Codes, gives the bit values for the status codes returned by the disk drive. Table 6o4 Status Codes Descriptions of the status codes are given below: GOOD - This status byte indicates that the operation completed as expected. CHECK CONDITION - Any error, exception, or abnormal condition, that causes sense data to be set causes a CHECK CONDITION status. The REQUEST SENSE command should be issued following a CHECK CONDITION status to determine the condition. NOTE: If any command other than REQUEST SENSE or INQUIRY is issued following a CHECK CONDITION, the sense data is lost. BUSY - The drive returns this status whenever it is unable to accept a command. For example, the drive returns this Doc 1015586, Rev B 8 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual status when it is busy doing self-tests and self configuration after being powered up or reset, or if the drive is busy executing a previously received command. INTERMEDIATE-GOOD - This status is returned for every command in a series of linked commands (except the last command), unless an error, exception, or abnormal condition, causes a CHECK CONDITION status or a RESERVATION CONFLICT status to be set. If the INTERMEDIATE-GOOD status is not returned, the chain of linked commands is broken; no further commands in the series are executed. RESERVATION CONFLICT - This status is returned whenever an initiator attempts to access a drive that is reserved by another initiator. 6.5.6 MESSAGE Phase The MESSAGE phase is used to transfer information about exception conditions between the initiator and the drive. The MESSAGE IN and MESSAGE OUT phases are discussed below, followed by descriptions of the SCSI messages. Message codes supported by the drive are shown in Table 6o5, Message Codes. Table 6o5 Message Codes 6.6 SCSI MESSAGES 6.6.1 MESSAGE IN Phase During the MESSAGE IN phase, a message is transferred from the drive to the initiator. The drive may enter this phase at any time. 6.6.2 MESSAGE OUT Phase During the MESSAGE OUT phase, a message is transferred from the initiator to the drive. The initiator requests that the drive enter the MESSAGE OUT phase by asserting the -ATN line. The drive frequently monitors the -ATN line and enters the MESSAGE OUT phase at its earliest Doc 1015586, Rev B 9 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual convenience in response to the initiator's assertion of - ATN. After being selected, the drive sets the control lines in preparation for the MESSAGE OUT phase. If the initiator has -ATN asserted, the drive requests a message from the initiator by asserting -REQ. The first message is expected to be an IDENTIFY message, but the drive also accepts a BUS DEVICE RESET, or an ABORT message. If any other message is received the drive goes to the BUS FREE phase. (See 6.6.16 SYNCHRONOUS DATA TRANSFER REQUEST Message later in this chapter for additional information.) If, during the selection, the initiator does not assert its ID on the bus, the drive does not examine the -ATN signal. The drive assumes the initiator cannot support any message except COMMAND COMPLETE, and does not support DISCONNECT-RECONNECT. The drive also assumes the initiator ID is zero, and saves any status for that initiator as initiator zero. NOTE: If the initiator expects the drive to disconnect- reconnect, then a MESSAGE OUT phase (the IDENTIFY message with bit six true) must occur immediately following a SELECTION phase which had both the initiator's, and the drive's, SCSI device ID asserted on the bus. 6.6.3 COMMAND COMPLETE (00h) The COMMAND COMPLETE message is sent from the drive to the initiator to indicate that the execution of a command (or a series of linked commands) has terminated, and that valid status has been sent to the initiator. After sending this message successfully, the drive goes to the BUS FREE phase by releasing -BSY, unless the initiator sets the -ATN line. NOTE: The command may or may not have been executed successfully, as indicated in the status. If the initiator rejects this message with a MESSAGE REJECT message, the drive goes to the BUS FREE phase and does not consider this an error. 6.6.4 SAVE DATA POINTER (02h) When doing disconnects, the SAVE DATA POINTER message is sent before every DISCONNECT message . If the initiator rejects this message with a MESSAGE REJECT message, the drive does not disconnect. Doc 1015586, Rev B 10 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.6.5 RESTORE POINTERS (03h) The RESTORE POINTERS message is sent from the drive to the initiator. The message acts to restore to the active state the most recently saved pointers for the currently attached logical unit. Pointers to the command, data, and status locations for the logical unit are restored to the active pointers. Command and status pointers are restored to the beginning of the present command and status areas. The data pointer is restored to the value at the beginning of the data area, or to the value at the point at which the last SAVE DATA POINTERS message occurred for that logical unit. If the initiator rejects this message with a MESSAGE REJECT message, the drive immediately terminates the present command with a CHECK CONDITION status and sets the sense data to HARDWARE ERROR/MESSAGE REJECT ERROR (04h, 43h) for that initiator. When the drive reselects the initiator, the IDENTIFY message implies that the initiator should restore its pointers. Therefore, this message is not normally used in reselection. 6.6.6 DISCONNECT (04h) This message is sent by the drive to inform the initiator that the present physical path is about to be broken (the drive plans to disconnect by releasing -BSY), but that a later reconnect is required in order to complete the current operation. This message does not cause the initiator to save the data pointer. If the initiator rejects this message with a MESSAGE REJECT message, the drive does not disconnect. 6.6.7 INITIATOR DETECTED ERROR (05h) The INITIATOR DETECTED ERROR message is issued by an initiator to inform the drive that an error has occurred during an operation. This message should be sent by the initiator when a parity error is detected. 6.6.8 ABORT (06h) The ABORT message is sent from the initiator to the drive to clear the present operation. All pending data and status for the issuing initiator is cleared from the drive, and the drive goes to the BUS FREE phase. Pending data and status for other initiators is not cleared. No status or ending message is sent for the operation. It is Doc 1015586, Rev B 11 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual not an error to issue this message to a logical unit that is not currently performing an operation for the initiator. 6.6.9 MESSAGE REJECT (07h) The MESSAGE REJECT message is sent from either the initiator or the drive to indicate that the last message received was inappropriate or has not been implemented. To create a MESSAGE REJECT message the initiator asserts - ATN prior to releasing -ACK; the handshake of the message is then rejected. When the drive sends this message it changes to the MESSAGE IN phase and sends this message prior to requesting additional message bytes from the initiator. This provides an interlock so that the initiator can determine which message is rejected. If the initiator responds to this message with a MESSAGE REJECT message, the drive immediately terminates the present command with a CHECK CONDITION status and sets the sense data to HARDWARE ERROR/MESSAGE ERROR (04h, 43h) for that initiator. 6.6.10 NO OPERATION (08h) The initiator sends the NO OPERATION message when it has no valid message for the drive request. The drive receives and ignores this message. 6.6.11 MESSAGE PARITY ERROR (09h) The initiator sends a MESSAGE PARITY ERROR message to indicate a parity error on one or more bytes of the last message sent from the drive. The initiator asserts -ATN prior to releasing -ACK for the last byte of the message in error, so that the drive knows which message is in error. The drive resends the message. If the Message Parity Error is received again, the drive goes to the BUS FREE phase and aborts the current command for that initiator. No further reconnection is attempted, and neither STATUS nor COMMAND COMPLETE messages are returned for the command. The sense data is set to ABORTED COMMAND/SCSI PARITY ERROR (04h, 47h) for that initiator. Doc 1015586, Rev B 12 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.6.12 LINKED COMMAND COMPLETE (0Ah) The LINKED COMMAND COMPLETE message is sent to the initiator to indicate that the execution of a linked command has completed and that the status has been sent. If the initiator responds with a MESSAGE REJECT message, the drive goes to the BUS FREE phase and does not execute the next command. The sense data is set to HARDWARE ERROR/MESSAGE ERROR (04h, 43h) for that initiator. 6.6.13 LINKED COMMAND COMPLETE (WITH FLAG) (0Bh) The LINKED COMMAND COMPLETE (WITH FLAG) message is sent to the initiator to indicate that the execution of a linked command (with the flag bit set to one) has completed and that the status has been sent. If the initiator responds with a MESSAGE REJECT message, the drive goes to the BUS FREE phase and does not execute the next command. The sense data is set to HARDWARE ERROR/MESSAGE ERROR (04h, 43h). 6.6.14 BUS DEVICE RESET (0Ch) An initiator may send the BUS DEVICE RESET message to the drive to clear all current commands on that SCSI device. The drive clears all commands, goes through its initial power up checks, its self configuration, and goes to the BUS FREE condition ("hard" RESET). 6.6.15 IDENTIFY (C0h/80h) The IDENTIFY message is sent by an initiator after it selects a drive. It is sent by the drive as the first message after a reconnection. In addition, this message specifies that the sender supports some or all of the optional messages. The bits in Table 6o6, IDENTIFY Message Codes, show that the only truly changeable bit is bit six; therefore, the command can have only two values: C0h if the disconnect/reconnect feature is supported, or 80h if the disconnect/reconnect feature is not supported. Table 6o6 IDENTIFY Message Codes Doc 1015586, Rev B 13 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual If the initiator responds to this message with a MESSAGE REJECT message, the drive immediately terminates the present command with a CHECK CONDITION status and sets the sense key/error code to HARDWARE ERROR/Message Reject Error (04h, 43h) for that initiator. NOTE: The drive does not disconnect if, during the SELECTION phase, the initiator does not set its initiator SCSI device ID on the bus, and if the initiator does not send an IDENTIFY message out (with bit six set) to the drive. 6.6.16 SYNCHRONOUS DATA TRANSFER REQUEST Message (01h) The drive can, optionally, perform synchronous data transfers, as discussed in 6.5.2 Synchronous Data Transfer earlier in this chapter. A pair of SYNCHRONOUS DATA TRANSFER REQUEST messages (see Table 6o7 SYNCHRONOUS DATA TRANSFER REQUEST Byte Values) are exchanged between an initiator and the drive under the following conditions: o a SCSI device that supports synchronous data transfer recognizes it has not communicated with the other SCSI device since receiving the last "hard" RESET o A SCSI device that supports synchronous data transfer recognizes it has not communicated with the other SCSI device since receiving a BUS DEVICE RESET message SCSI devices may also exchange messages to establish synchronous data transfer when requested to do so. The messages exchanged establish the transfer period and the -REQ/-ACK offset. Table 6o7 SYNCHRONOUS DATA TRANSFER REQUEST Byte Values The transfer period is defined as the minimum time between the leading edge of a -REQ pulse and of its corresponding -ACK pulse. The -REQ/-ACK offset is defined as the maximum number of -REQ pulses that may be outstanding before the corresponding -ACK pulse is received at the drive. A -REQ/-ACK offset value of zero indicates asynchronous mode; a value of 0Fh yields the maximum number of outstanding -REQ pulses supported (fifteen). If the initiator recognizes that negotiation is required, it asserts -ATN and, if the drive implements message transfers, sends a SYNCHRONOUS DATA TRANSFER REQUEST Doc 1015586, Rev B 14 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual message, specifying the -REQ/-ACK offset and minimum transfer period. The -REQ/-ACK offset is chosen to meet the data handling requirements of the target, while the minimum transfer period is chosen to meet the data handling requirements of the initiator. The drive responds in any of the ways outlined in Table 6o8, Drive Responses to the SYNCHRONOUS DATA TRANSFER REQUEST Message. Table 6o8 Drive Responses to the SYNCHRONOUS DATA TRANSFER REQUEST Message The implied agreement remains in effect until a BUS DEVICE RESET message is received, a "hard" RESET condition occurs, or until one of the two SCSI devices elects to modify the agreement. Renegotiation at every selection is not recommended since a significant performance impact is likely. The default mode of data transfer is asynchronous. The default mode is entered at power on, after a BUS DEVICE RESET message, or after a "hard" RESET condition. The SYNCHRONOUS DATA TRANSFER REQUEST message exchange can only take place following a SELECTION phase that includes the SCSI IDs for both the initiator and the target. Violation of this rule may make data transfer impossible owing to disagreements among SCSI devices about the data transfer mode. 6.7 ERROR CONDITIONS Under several error conditions, the drive changes the phase to BUS FREE without correctly terminating the command (i.e., no DISCONNECT or COMMAND COMPLETE message is sent). The drive clears all information regarding the command, except sense data (if any), and does not attempt to reconnect, or in any other way terminate, the command. The initiator must assume that this is a catastrophic failure and return the error to the system software. Sense data may or may not be valid when this condition occurs. If the initiator issues a REQUEST SENSE command and the returned sense key and additional sense code are not zero, the sense data is valid. Doc 1015586, Rev B 15 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.7.1 MESSAGE OUT Phase Parity Error If the drive detects a parity error during the MESSAGE OUT phase it retries the MESSAGE OUT phase once using the following sequence: 1. Continue the -REQ/-ACK handshake until the initiator negates -ATN (receives all of the message bytes). 2. Instruct the initiator to resend all of the message bytes sent during the previous MESSAGE OUT phase by not changing the phase and asserting -REQ. 3. The initiator then resends all of the previous message bytes. If, after one retry, the message is still not received correctly, the drive processes the error using one of the following sequences: o If an IDENTIFY message is not received, the drive immediately goes to the BUS FREE phase. No sense data code information is set for this type of error. o If an IDENTIFY message is received, the drive terminates the present command with a CHECK CONDITION status and sets the sense data to ABORTED COMMAND/SCSI PARITY ERROR (0Bh/47h). This error does not prevent the initiator from retrying the command. 6.7.2 COMMAND Phase Parity Error When the drive detects a parity error during the COMMAND phase, it retries the COMMAND phase one time using the following sequence: 1. Send the initiator a RESTORE POINTERS message to reset the pointers to the start of the command. 2. Attempt to receive the entire command again. If, after one retry, the command is still not received successfully, the drive aborts the command using one of the following sequences: o If the initiator does not send an IDENTIFY message, the drive immediately goes to the BUS FREE phase. No sense data information is sent for this type of error. o If the drive receives an IDENTIFY message, it terminates the command with a CHECK CONDITION status and sets the sense data to ABORTED COMMAND/SCSI PARITY Doc 1015586, Rev B 16 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual ERROR (0Bh/47h). This error does not prevent the initiator form retrying the command. 6.7.3 DATA OUT Phase Parity Error If the drive detects a parity error during the DATA OUT phase, it terminates the command with a CHECK CONDITION status, and sets the sense data to ABORTED COMMAND/SCSI PARITY ERROR(0Bh/47h). This error does not prevent the initiator from retrying the command. 6.7.4 Initiator Detected Error If the drive receives an initiator detected error message at any time during the command, except during the STATUS phase or COMMAND COMPLETE message, it terminates the current command with a CHECK CONDITION status and sets the sense data to ABORTED COMMAND/INITIATOR DETECTED ERROR MESSAGE RECEIVED(0Bh/48h). This error does not prevent the initiator from retrying the command. If the initiator sends an initiator detected error message immediately after the STATUS phase, the drive sends a RESTORE POINTERS message and resends the status. If the initiator sends another initiator detected error message in response to the resent status, the drive immediately goes to the BUS FREE phase. The sense data is set to ABORTED COMMAND/INITIATOR DETECTED ERROR MESSAGE RECEIVED(0Bh/48h). This error does not prevent the initiator from retrying the command. If the initiator sends an initiator detected error message immediately after the COMMAND COMPLETE message is sent, the drive immediately goes to the BUS FREE phase. The sense data is set to ABORTED COMMAND/INITIATOR DETECTED ERROR MESSAGE RECEIVED(0Bh/48h). This error does not prevent the initiator from retrying the command. 6.7.5 REJECTED Message When the drive receives a MESSAGE REJECT message from the initiator, it resends the original message. If the message is rejected again, the drive takes one of the following actions, based on which message was rejected: o COMMAND COMPLETE - If the rejected message is a COMMAND COMPLETE message, the disk drive goes to the BUS FREE phase and does not consider this an error. Doc 1015586, Rev B 17 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual o DISCONNECT - If the rejected message is a DISCONNECT message, the drive does not disconnect from the initiator and continues the current command. This condition does not preclude the drive from attempting to disconnect at a later time. NOTE: The drive does not send a DISCONNECT message to an initiator which does not support the disconnect/reconnect option. o IDENTIFY (Reconnect) - If the rejected message is an IDENTIFY message, the drive immediately goes to the BUS FREE phase and aborts the current SCSI command. No further reconnection is attempted, and no STATUS or COMMAND COMPLETE message is sent for the command. The sense data is set to HARDWARE ERROR/MESSAGE ERROR(04h/43h). o LINKED COMMAND COMPLETE - If the rejected message is a LINKED COMMAND COMPLETE message, the drive immediately goes to the BUS FREE phase and does not read the next command in the linked list. The sense data is set to HARDWARE ERROR/MESSAGE ERROR(04h/43h). o MESSAGE REJECT - If the rejected message is a MESSAGE REJECT message, the drive immediately terminates the present command with a CHECK CONDITION status and sets the sense data to HARDWARE ERROR/ MESSAGE ERROR (04h/43h). o RESTORE POINTERS - Since the RESTORE POINTERS message is only used in an error recovery or retry situation, if the rejected message is a RESTORE POINTERS message, the drive aborts the recovery or retry attempt, assumes the error is unrecoverable, and completes the command according to the error condition. o SAVE DATA POINTER - The drive assumes the initiator does not support this message and does not attempt to disconnect from the bus during this command. 6.7.6 Initiator MESSAGE PARITY ERROR When the drive receives a MESSAGE PARITY ERROR message from the initiator, it retries the operation by resending the original message. If the message cannot be sent successfully, the drive immediately goes to the BUS FREE phase and aborts the current SCSI command. No further reconnection is attempted and no STATUS or COMMAND COMPLETE message is returned for the command. The sense data is set to ABORTED COMMAND/SCSI PARITY ERROR (0Bh/47h). Doc 1015586, Rev B 18 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 6.7.7 RESELECTION Time-Out When the drive attempts to reselect the initiator and the initiator does not respond within a selection time-out delay (as defined in the SCSI standard), the reselection is aborted. The drive attempts the reselection 254 more times and, if all attempts fail, the drive aborts the current SCSI command. No further reconnection is attempted, and no STATUS or COMMAND COMPLETE message is returned for the command. The sense data is set to HARDWARE ERROR/SELECT/RESELECT FAILURE (04h/45h). NOTE: The initiator must have an overall command time-out delay to detect this error. 6.7.8 Internal Controller Errors If an error occurs within the embedded controller that is related to the SCSI hardware or firmware, the drive terminates the present command with a CHECK CONDITION status and sets the sense data to HARDWARE ERROR/INTERANALTARGET FAILURE (04h/44h). This error does not prevent the initiator from retrying the command. Doc 1015586, Rev B 19 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 217 Maxtor Corporation Doc 1015586, Rev B 217 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual APPENDIX A: THE READ-AHEAD FEATURE WHAT IS READ-AHEAD? Read-Ahead is a form of data caching where data is read from the disk to the buffer in anticipation of future operations. This feature can greatly improve system access times and throughput in many applications by reducing the time required to make data available to the host. Read-Ahead can be switched on or off by means of the MODE SELECT command. HOW DOES IT WORK? To understand how Read-Ahead works, it is first useful to examine how data is stored in typical systems applications. The tracks on a drive are divided into sectors as the smallest addressable unit of storage. Data is stored as files of various lengths, with one sector as a minimum, but most files are spread across a number of sectors. When a file spans multiple sectors, it can be stored and retrieved most quickly if the sectors are written consecutively, and so most operating systems allocate a contiguous group of sectors to a file, and write the data in a sequential fashion within this allocated area. Thus, although the drive is a random- access device, files tend to be localized, and much of the data transferred is sequential. As applications use larger files (such as the multimegabyte graphics images created by CAD workstations), disk accesses tend to become more sequential. When retrieving a file stored in this way, the highest performance is achieved if a single READ command is issued, with the transfer length field set to the full length of the file. In reality, however, this is rarely the case. In operating systems such as UNIX, READ commands are usually issued with a fixed transfer length (typically 1 to 8 kilobytes), and several successive commands are required to retrieve larger files. When an access of many sectors is broken up into smaller commands, it is not possible to transfer the data in the most efficient way, because the time delay between the completion of one command and the beginning of the next is much longer than the gap time between adjacent sectors. By the time the next command has Doc 1015586, Rev B 218 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual been received, the disks have already rotated beyond the start of the next consecutive sector, so it is usually necessary to wait for nearly a full latency period before the disk drive is able to continue the data transfer. Obviously, this additional latency increases the time required to read the entire file, and significantly degrades performance. As an example, consider the situation shown in Figure Ao1, Sequential READs without Read-Ahead. 1. the host issues a command to read sectors zero and one 2. some amount of latency is required to arrive at the starting sector 3. data is read from the disk to the data buffer 4. when one full sector is available in the buffer the drive starts to transfer data to the host 5. after all the data has been sent to the host and status information has been provided, the host prepares to send the next command 6. the second command (requesting a READ of sectors two and three) arrives, well after the heads have passed the start of sector two: almost a full revolution is required before sector two rotates back around to the read/write head Figure Ao1 Sequential READs without Read-Ahead Read-Ahead avoids the loss of performance represented by step five by taking advantage of the disk drive's idle time to read additional data into the buffer. There it is available for immediate transfer in the event that the next READ command requests blocks which are already in the buffer. The probability of a "hit" (a match between data requested and data in the buffer) is relatively high in systems which store data contiguously. When the initiator sends a READ command to the drive, it appears to complete normally. In the background, however, while the system is obtaining status and preparing to send the next command, the disk drive continues to read data from the disk to the buffer. If the next command is also a READ, the disk drive checks to see if the requested data is in the buffer, and if Doc 1015586, Rev B 219 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual so, the data is transferred to the host immediately, without a delay for rotational latency. Of course, not all READ commands request contiguous sectors, so it is important that the Read-Ahead feature not impair performance when it is not needed. For example, if the disk drive is reading ahead and the next command received is anything other than a READ command (e.g. WRITE, SEEK, etc.), or the new command is a READ command for logical blocks which are not already in the buffer, the Read-Ahead operation immediately aborts and the new command is executed. Additionally, the host system can disable Read-Ahead via the MODE SELECT command if it is known that data accesses will be largely random rather than sequential. This technique avoids the overhead (approximately 100 microseconds) associated with checking the buffer to see if requested data is already present. KEY READ-AHEAD PARAMETERS Size of Read-Ahead Buffer: The Read-Ahead buffer has 45 kilobytes. This is equivalent to approximately one and a half tracks. When Invoked: If enabled, Read-Ahead is automatically performed after every READ or READ (EXTENDED) command. When Aborted: Read-Ahead is aborted for any of the following reasons: o the buffer has been filled with 45 kilobytes of data o a new command is received which is not a READ command, or which requires an access to a different area of the disk o a data error occurs while reading ahead o a SEEK is required to continue reading ahead (e.g., a cylinder boundary is encountered) with the RAMD bit set to zero in page code 38h CONTROLLING THE READ-AHEAD FEATURE The Read-Ahead feature is controlled by either setting the read cache disable bit (RCD) to zero in the caching page (page code 08h) or by setting the cache enable bit (CE) to one in the read-ahead control page (page code 38h). See Table 7o29 or Table 7o43. Doc 1015586, Rev B 220 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual READ ALGORITHM The sequence of a READ command varies depending on the answers to the following questions: (a) is Read-Ahead enabled? (b) is the READ command requesting data which has been prefetched? and (c) does the transfer length exceed the range of data which has been prefetched, thus requiring a media access? See Table Ao1, READ Algorithm. Table Ao1 READ Algorithm READ-AHEAD PERFORMANCE The performance benefits of Read-Ahead vary depending on the operating system and application programs. The greatest benefits will be seen in UNIX-based systems which transfer large blocks of data with few users (e.g., graphics workstations), and the least benefit will be seen in systems with many users and short files (e.g., transaction processing). The greater the randomness of disk accesses, the less likely that the next command will request data that has been prefetched. Doc 1015586, Rev B 221 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 223 Maxtor Corporation Doc 1015586, Rev B 223 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual APPENDIX B: DISCONNECT/RECONNECT CONDITIONS This appendix describes the conditions under which the disk drive disconnects from, and reconnects to the SCSI bus. These are the default options provided by the disk drive, but may be modified by the initiator using the MODE SELECT command. The normal DISCONNECT/RECONNECT options stress maximum throughput, yet do not monopolize the SCSI bus, providing maximum bus use. These options would be used in a multiple initiator environment. Also, the initiator should be capable of sustaining a SCSI bus throughput which is equal to, or greater than, the disk drive's internal data transfer rate. To disable disconnects, the initiator should not set bit six in the ID message that it sends at the start of a command. If the disk drive is processing a command which does not support disconnects (bit six in the ID message equals zero), and any other command is active, the disk drive immediately terminates the command that cannot disconnect with a BUSY status. If normal system operation includes multiple commands sent to the disk drive simultaneously, the initiator should enable the DISCONNECT/RECONNECT option (bit six in the ID message set to one). The disconnect/reconnect conditions are as follows: o When the SCSI bus is anticipated to be idle (no -REQ is active) for the amount of time specified in the MODE SELECT command bus inactivity limit field, the disk drive automatically disconnects from the SCSI bus. o When a disk drive receives a command while a command from another initiator is active, the disk drive disconnects from the bus as soon as the entire command from the initiator has been received. o READ commands always disconnect immediately after receipt of the command. This allows access to the SCSI bus during the disk latency and/or seek time. o When executing a READ command, if the disk drive anticipates that the bus will be idle for longer than the time specified in the MODE SELECT bus inactivity limit field, the disk drive disconnects from the bus as soon as the bus becomes idle. The disk drive then reconnects when data is available to be transferred. This condition may occur if: 1) Doc 1015586, Rev B 224 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual the read operation crosses a cylinder boundary and a seek operation is required; 2) a seek operation to an alternate track is required; or 3) the SCSI data transfer rate is greater than the disk drive's internal data transfer rate and the buffer has been emptied. o When the drive receives a WRITE command, it reads data from the initiator until the internal buffer is filled. Once the buffer is filled, or all the data has been transferred, the disk drive disconnects from the bus. The reconnect occurs when the disk drive starts to write data to the disk, and the internal buffer becomes available for more data to be transferred from the initiator. A reconnect also occurs, after all the data has been written to the disk, to return the status and terminate the command. Doc 1015586, Rev B 225 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual Doc 1015586, Rev B 227 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual APPENDIX C: DEFECT MANAGEMENT There are four different ways in which defects can be managed in the XT-8000S Family disk drives: o Cylinder-Oriented. Each cylinder is an integral unit, with the alternates per zone number of spares assigned to the cylinder. A defect anywhere within the cylinder is reassigned by invoking one of the spare sectors, which are initially located at the end of the last track of the cylinder. If the number of reassigned sectors exceeds the number of spare sectors, one track of the cylinder is relocated to the area of the disk drive defined by the alternate tracks per volume field. o Track-Oriented. Each track is an integral unit, with one or more spares assigned to the track. A defect anywhere within the track is reassigned by invoking one of the spare sectors, which are initially located at the end of the track, just prior to index. If the number of reassigned sectors exceeds the number of spare sectors, the track is relocated to the area of the disk drive defined by the alternate tracks per volume field. o Disk Drive-Oriented. The entire drive is an integral unit, with the alternates per zone number of spares assigned to the disk drive. A defect anywhere on the disk drive is reassigned by relocating the sector to one of the spare sectors, which are located in the area of the disk drive defined by the alternate tracks per volume field. o Host Defect Management. The entire drive is an integral unit, with no spares. A defect anywhere on the disk drive is deallocated by the host operating system, and future access to this sector are inhibited. An error occurs if you use the REASSIGN BLOCK command in this mode. Set the MODE SELECT values of tracks per zone, alternate sectors per zone, and alternate tracks per volume, as shown in Table Co1, Defect Management Selections, to choose one of the four techniques. Table Co1 Defect Management Selections XT-8000S Product Specification & OEM Technical Manual NOTE: The alternate sectors per zone, and alternate tracks per volume, field values are recommended by Maxtor for most applications, but may vary per customer requirements of capacity versus performance. For example, if cylinder-oriented mode is selected, the systems integrator may elect to increase capacity by reserving fewer alternate sectors per zone. This increases the probability that a track may have to be relocated because of more defects than spares in a given cylinder, so the number of alternate tracks per volume may need to be increased. Also, performance may be degraded as a result of the additional SEEKs imposed by track relocation. REASSIGNMENT SEQUENCES When a defective area is found, a reassignment algorithm is invoked by either the REASSIGN BLOCK or FORMAT UNIT command, and multiple blocks may be reassigned in one operation. For simplicity, the following reassignment sequences assume a single block reassignment. Cylinder-Oriented Reassignment Sequence 1. The designated block is located, and the entire cylinder in which it resides is verified to ensure that there are no unflagged defects. 2. The cylinder is copied to the reserved cylinder (MAX-1). 3. Flags in the configuration area (cylinder zero) are updated, to indicate completion of the first phase in case a power failure or RESET interrupts the process. 4. The affected cylinder is reformatted, with the headers updated to "slip" the bad block and all following blocks (up to the end of the cylinder) by one. This causes some logical blocks to move from the last position on one track to the first position on the next track, but all blocks are contiguous within the cylinder. 5. Flags in the configuration area are updated to indicate completion of the second phase. 6. The content of the reserved cylinder is copied back to the original cylinder. Doc 1015586, Rev B 229 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual 7. Flags in the configuration area are updated to indicate completion of the operation. In the event that there are insufficient spares in the cylinder, one of the tracks in the cylinder is relocated to the area defined by the alternate tracks per volume. These are located in the area ending with cylinder MAX-2 (the starting cylinder depends on the number of alternate tracks, which is always a multiple of the number of heads). This restores to the cylinder those spares which had been consumed by the defects in this track, and reduces the probability that a future reassignment in the same cylinder results in a track relocation. When a SEEK is performed to an LBA which has been reassigned, the following sequence applies: 1. The drive SEEKs to the cylinder and head where the sector was originally located, and begins a search for the header. 2. Upon reading the first header encountered, the disk drive determines whether the target sector is within the current track. Information in the header indicates the number of the last sector on the current track, and whether the track has been relocated. 3. If the target sector was once the last one on a track, and has been rolled over to the next track in the cylinder due to a reassignment, this is detected from the "last sector" information in the header that was read, and a head switch is performed immediately. 4. If the track has been relocated, the disk drive SEEKs to the alternate area. If the data transfer is long enough to go beyond the end of the track, a SEEK back to the original cylinder takes place to continue the transfer. Track-Oriented Reassignment Sequence 1. The designated block is located, and the entire track in which it resides is verified, to ensure that there are no unflagged defects. 2. The track is copied to a track in the reserved cylinder (MAX-1). XT-8000S Product Specification & OEM Technical Manual 3. Flags in the configuration area (cylinder zero) are updated, to indicate completion of the first phase in case a power failure or RESET interrupts the process. 4. The affected track is reformatted, with the headers updated to "slip" the bad block and all following blocks (up to the end of the track) by one. All blocks are contiguous within the track. 5. Flags in the configuration area are updated to indicate completion of the second phase. 6. The content of the reserved area is copied back to the original track. 7. Flags in the configuration area are updated to indicate completion of the operation. In the event that there are insufficient spares in the track, the entire track is relocated to the area defined by the alternate tracks per volume field. When a SEEK is performed to an LBA which has been reassigned, the following sequence applies: 1. The disk drive SEEKs to the cylinder and head where the sector was originally located, and begins a search for the header. 2. Upon reading the first header encountered, the drive determines whether the track has been relocated. 3. If the track has been relocated, the disk drive SEEKs to the alternate area. If the data transfer length extends beyond the end of the relocated track, a SEEK back to the original cylinder takes place to continue the transfer. Disk Drive-Oriented Reassignment Sequence 1. The designated block is copied to a sector in the reserved cylinder (MAX-1). 2. The header of the designated block is written with a pattern which indicates that it has been relocated. In the event that there are insufficient spares in the reserved area, the disk drive returns an error condition indicating that no spares are available. Doc 1015586, Rev B 231 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual When a SEEK is performed to an LBA which has been reassigned, the following sequence applies: 1. The drive SEEKs to the cylinder and head where the sector was originally located, and begins a search for the header. 2. Upon reading the target header, the disk drive determines that the sector has been relocated. 3. The disk drive SEEKs to the alternate area to access the requested LBA. A SEEK back to the original cylinder takes place to continue the transfer, if necessary. Host Defect Management Sequence 1. The defective block is allocated to either a dummy file or a "bad block" list. 2. The host ensures that no accesses are performed to the defective block. DEFECT MANAGEMENT ASSUMPTIONS AND STATISTICS In order to choose a defect management mode, it may be useful to examine some of the assumptions and statistics which affect the media. The number of spares allocated must include the sum of: o the initial maximum number of defects specified by the manufacturer (that is, primary defects) o the additional defects which accumulate during the life of the drive (that is, grown defects) The following tables, Table Co2 and Table Co3, illustrate the effect of spares and defects on capacity. Table Co2 Spares Versus Capacity, XT-8380 XT-8000S Product Specification & OEM Technical Manual Table Co3 Spares Versus Capacity, XT-8760 Doc 1015586, Rev B 233 Maxtor Corporation XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual APPENDIX D: CDB BIT DEFINITIONS Abbreviation Meaning ARRE automatic read reallocation enabled bit AWRE automatic write reallocation enabled bit BytChk byte check bit DCR disable correction bit DCRT disable certification bit DevOfl device off-line bit DPRY disable primary bit DT defective track bit DTE disable transfer on error bit EEC enable early correction bit FmtData format data bit FOV format options valid bit HSEC hard sector format bit ILI incorrect length indicator bit Immed immediate bit INS inhibit save bit PCF page control field bit PER post error bit PF page format bit PMI partial medium indicator bit PS parameters saveable bit RC read continuous bit RelAdr relative address bit RMB removable media bit SlfTst self-test bit SP save parameters bit SS spare sector bit SSEC soft sector format bit STPF stop format bit SURF surface bit TB transfer block bit 3rdPty third party reservation bit UntOfl unit off-line bit VU vendor unique bit WP write protect bit XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual XT-8000S Product Specification & OEM Technical Manual APPENDIX E: UNITS OF MEASURE Abbreviation Meaning A/m amps per meter AWG American wire gauge bpi bits per inch dBa decibel, A-weighted fci flux changes per inch g gram Gbyte gigabyte Hz hertz mA milliamp A microamp Mbit megabit Mbyte megabyte m micrometer msec millisecond sec microsecond nsec nanosecond Oe oersted RH relative humidity rpm revolutions per minute tpi tracks per inch xxb binary values xxh hexadecimal values APPENDIX F: BUFFER RATIO APPLICATIONS WHAT ARE THE BUFFER RATIOS? The Buffer Ratios indicate to the target how full, on a READ command, or how empty, on a WRITE command, the buffer should be prior to attempting reselection. SCSI MODE SELECT parameter page 2 defines the Buffer Ratio parameters as numerators of a fractional multiplier that has 256 (FFh) as its denominator. A value of 128 (80h) would equate to a ratio of 50%, and 192 (C0h) equates to a ratio of 75%, etc. In standard SCSI, the percentage is applied to the total size of the data buffer. In Maxtor's implementation of the Buffer Ratios, the percentage is applied to either the data buffer or the data transfer, whichever is less. In other words, if the data transfer is less than the disk buffer, the Buffer Ratio will be applied to the transfer length. If the data transfer is greater than the disk buffer, the Buffer Ratio will be applied to the disk buffer. This implementation allows one value be used for the Buffer Ratios, regardless of the data transfer length. WHAT ARE THE PERFORMANCE BENEFITS FROM BUFFER RATIOS? The performance benefit from the Buffer Ratios is in a multi-target environment where SCSI "on-bus" time is critical. The Buffer Ratios ensure that the time on the SCSI bus is minimized and the data transfer rate across the SCSI bus is maximized. BUFFER FULL RATIO Without the Buffer Full Ratio the target would reconnect to the SCSI bus as soon as data is in the buffer. If the SCSI bus transfer rate is higher then the disk transfer rate, the transfer rate across the SCSI bus will slow to that of the disk. This will increase the total time on the bus for a given data transfer. Figure Fo1. shows this condition where the "Hold-off Time" is minimal and the "Total Time on Bus" is significant. Note that if the SCSI bus transfer rate is lower than the disk transfer rate, the Buffer Full Ratio should be zero (disabled). This will optimize performance in slower systems and is the default value for the Buffer Ratios. Figure Fo1 Data Transfer Rate Without Buffer Full Ratio With Buffer Full Ratio, the target will "Hold off" reconnecting to the bus until the desired percentage of data is in the buffer to ensure that the maximum SCSI bus rate can be achieved. This maximizes the SCSI bus rate and minimizes total "On-Bus" time. Figure Fo2. shows that by increasing the "Hold-off Time" the SCSI bus transfer rate is maximized and the "Total Time on Bus" is minimized, with the "Total Time to Data" remaining the same. Minimizing the total "On bus" time is essential for performance in a multi-target environment. Figure Fo2 Data Transfer Rate With Buffer Full Ratio BUFFER EMPTY RATIO The Buffer Empty Ratio applies to how empty of Write Data the buffer should be before reconnecting to obtain more Write Data. Maxtor's SCSI implementation "pre- reads" Write Data into the data buffer directly after the WRITE command is decoded. Because the size of the data buffer is 45,056 bytes the Buffer Empty Ratio will only apply to WRITE commands with data transfers over 45,056 bytes per command and a disconnect/reconnect is required for the remaining data. If WRITE commands have long data transfers, it is recommended that the Buffer Full Ratio and the Buffer Empty Ratio be Equal. WHAT VALUE SHOULD BE USED FOR THE BUFFER RATIOS? The value chosen for the Buffer Ratios should be selected to optimize the difference between the disk speed and the SCSI bus speed. In Figures Fo1 and Fo2, the difference in speed between the disk data rate and the SCSI bus are reflected by a difference in slopes, with a steep slope representing a higher speed. Table Fo1 below shows the calculated values for the Buffer Ratios with the given SCSI bus speed. Table Fo1 Buffer Ratio Values GLOSSARY ack. Acknowledge ADR. Address ANSC. American National Standards Committee ANSI. American National Standards Institute arbitration winner. The arbitrating SCSI device which has the highest SCSI address. assert. A signal driven to the true state. async. Asynchronous BCV. Buffer control valid bit. Binary digit byte. Eight consecutive binary digits C/C. Continuous/composite (format) CCS. Common Command Set C/D. CONTROL/DATA signal CDB. Command descriptor block, the structure used to communicate requests from an initiator to a disk drive. cmd. Command connect. The function that occurs when an initiator selects a target to start an operation. CRC. Cyclic redundancy check CSA. Canadian Standards Association DB (7-0, P). Eight data-bit signals, plus a parity-bit signal, that form a data bus. DC. Direct current DCR. Disabled correction (signal) disconnect. The function that occurs when a target releases control of the SCSI bus allowing it to go to the BUS FREE phase. DMA. Direct memory access EBP. Erase bypass ECC. Error correction code ECL. Emitter-coupled logic EDAC. Error detection and correction EIA. Electrical Industry Association ENDEC. Encoder/decoder EPROM. Erasable programmable read only memory ERA. Erase all FCC. Federal Communication Commission FIFO. First-in, first-out storage and retrieval technique firmware. Computer programs encoded permanently into a ROM FW. Firmware G. Constant of gravitation gnd. Ground hard error. An error due to faulty equipment, transmission techniques, recording media, etc. HDA. Head disk assembly hex. Hexadecimal HW. Hardware initiator. A SCSI device, usually a host system, that requests that an operation be performed by another SCSI device. INTERMEDIATE status. A status code sent from a target to an initiator upon completion of each command in a set of linked commands, except for the last command in the set. I/O. Input and/or output ISG. Inter-sector gap ISO. International Standardization Organization LBA. Logical block address LED. Light-emitting diode logical thread. The logical path which exists between an initiator's memory and a bus device LUN, even though the physical path may be disconnected. logical unit. A physical or virtual device addressable through a target. LSB. Least significant byte LSTTL. Low power, Schotky transistor-transistor logic LUN. Logical unit number, an encoded 3-bit identifier for the logical unit. C. Microcomputer computer. Microcomputer MFM. Modified frequency modulation (encoding) MO. Magneto optics MSB. Most significant byte MSG. Message MTBF. Mean time between failures MTTR. Mean time to repair MZCAV. Maxtor Zoned Constant Angular Velocity (format) N.C. No connection negate. A signal driven to the false state nom. Nominal OEM. Original equipment manufacturer one. True signal value parity. A method of checking the accuracy of binary numbers PC. Polycarbonate PCB. Printed circuit board peripheral device. A peripheral that can be attached to a SCSI device PLL. Phase-locked loop PLO. Phase-locked oscillator PM. Preventive maintenance P/N. Part number POH. Power On hours P-P. Peak to peak PROM. Programmable read only memory PTRN. Pattern RAM. Random-access memory reconnect. The function that occurs when a target selects an initiator to continue an operation after disconnect. req. Request reserved. Bits, bytes, fields and code values that are set aside for future standardization. RLL. Run-length limited ROM. Read-only memory rsrv. Reserved R/W. Read and/or write SCSI. Small Computer Systems Interface SCSI address. The octal representation of the unique address (0 - 7) assigned to a SCSI device. SCSI ID. The bit-significant representation of the SCSI address, referring to one of the signal lines DB (7 - 0). status. One byte of information sent from a target to an initiator upon completion of each command. STD. Standard SW. Software sync. Synchronization, synchronous target. A SCSI device that performs an operation requested by an initiator, in this manual, usually a disk drive. tbd. To be determined. Values which are not defined as of the date this manual is published. TLA. Top level assembly TTL. Transistor-transistor logic typ. Typical UL. Underwriter's Laboratories, Inc. UNC. Unified National Coarse UNF. Unified National Fine VDE. Verband Deutscher Electrotechniker vendor unique. The bits, fields, or code values that are vendor specific. WORM. Write once read multiple XFER. Transfer zero. False signal code Rev B Anderson/Sandoval 10\16\93