DOSSEG
.MODEL SMALL
.STACK 200h
.CODE
.386
ASSUME CS:@CODE, DS:@CODE
Ideal
────────────────────────────────────────────────────────
OldInt dd 0 ;for the old DMA interrupt
BaseAddress dw 220h
IrqNumber db 7
DMANumber db 1
SampleSeg dw 0
SampleOff dw 0
FileName db "jamhot.sam",0
SamLength dw ?
STRUC DMAInfo
Page dw ?,?
Length dw ?,?
Offset dw ?,?
Next dw 0,0 ;changes 2nd one to a "2" if 2 buffers are needed
Current dw 0 ;0 or 1
ENDS DMAInfo
DMA DMAInfo <>
────────────────────────────────────────────────────────
;==================
;==- Interrupts -==
;==================
PROC DMAINT FAR
pusha
cli
mov dx,[cs:BaseAddress]
add dx,0eh
in al,dx ;acknowledge interrupt
xor [cs:DMA.Current],1
mov bx,[cs:DMA.Current]
add bx,bx
mov bx,[cs:bx + DMA.NEXT]
mov ax,[cs:bx + DMA.Page]
mov ah,al
mov cx,[cs:bx + DMA.Length]
mov dx,[cs:bx + DMA.Offset]
call TransferDma
mov al,20h
out 20h,al ;end of hardware interrupt
popa
sti
iret
ENDP DMAINT
;======================
;==- Start Transfer -==
;======================
PROC StartTransferDma NEAR
pusha
mov al,[cs:IrqNumber]
add al,8
cbw
shl al,2
mov bx,ax
push es
sub ax,ax
mov es,ax
mov ax,[es:bx]
mov [WORD LOW cs:OldInt],ax ; Grab the current interrupt
mov ax,[es:bx+2]
mov [WORD HIGH cs:OldInt],ax ; so we can restore it later
pop es
mov ax,[cs:DMA.Page]
mov ah,al
mov cx,[cs:DMA.Length]
mov dx,[cs:DMA.Offset]
mov al,5
out 0ah,al ;Mask off channel 1
xor al,al
out 0ch,al ;Clear byte pointer F/F to lowerbyte
mov al,49h
out 0bh,al ;Set transfer mode to DAC (ADC = 45h)
mov al,dl ;LSB of BASE_ADDRESS
out 2,al
mov al,dh ;MSB of BASE_ADDRESS
out 2,al
mov al,ah
out 83h,al ;Page Number
mov al,cl
out 3,al ;LSB of DATA_Length
mov al,ch
out 3,al ;MSB of DATA_Length
mov al,1
out 0ah,al ;Enable Channel 1
mov ax,offset DMAInt
call DoRealInt
mov al,14h ;function 14h DMAmode 8-bit DAC
call Sendcommand
mov al,cl ;send LSB of DATALENGTH
call SendCommand
mov al,ch ;send MSB of DATALENGTH
call SendCommand
popa
ret
ENDP StartTransferDma
;ah= page number
;dx= BASE_ADDRESS
;cx= DATA_LENGTH (-1)
PROC TransferDma NEAR
pusha
mov al,5
out 0ah,al ;Mask off channel 1
xor al,al
out 0ch,al ;Clear byte pointer F/F to lowerbyte
mov al,49h
out 0bh,al ;Set transfer mode to DAC (ADC = 45h)
mov al,dl ;LSB of BASE_ADDRESS
out 2,al
mov al,dh ;MSB of BASE_ADDRESS
out 2,al
mov al,ah
out 83h,al ;Page Number
mov al,cl
out 3,al ;LSB of DATA_Length
mov al,ch
out 3,al ;MSB of DATA_Length
mov al,1
out 0ah,al ;Enable Channel 1
mov al,14h ;function 14h DMAmode 8-bit DAC
call Sendcommand
mov al,cl ;send LSB of DATALENGTH
call SendCommand
mov al,ch ;send MSB of DATALENGTH
call SendCommand
popa
ret
ENDP TransferDMA
;ah= TC (Time Constant = 256 - 1,000,000/HZ)
PROC SetTimeConstant NEAR
mov al,40h
call SendCommand
mov al,ah
call SendCommand
ret
ENDP SetTimeConstant
PROC TurnOffSpeaker NEAR
mov al,0d3h ;turn off speaker
call Sendcommand
ret
ENDP TurnOffSpeaker
PROC HaltDMA NEAR
mov al,0d0h ;Halt DMA
call SendCommand
ret
ENDP HaltDma
;al = command
PROC SendCommand NEAR
push dx
push ax
mov dx,[cs:BaseAddress]
add dx,0ch
@@Sendcommandloop:
in al,dx
or al,al
js @@Sendcommandloop
pop ax
out dx,al
pop dx
ret
ENDP SendCommand
PROC TurnOnSpeaker NEAR
mov al,0d1h
call SendCommand
ret
ENDP TurnOnSpeaker
;input- none
;output al=0 successful
; al=1 unsuccessful
;DESTROYED: ax,dx,cx
PROC DspReset NEAR
mov dx,[cs:baseaddress]
add dx,06h
mov al,1
out dx,al
mov cx,1000
push di
rep lodsb ;wait for at least 3µS
pop di
xor al,al
out dx,al
add dx,8 ;check WhichBuffer (22eh)
mov cx,12000
waitforstat:
in al,dx
dec cx
je errorstat
test al,10000000b
jz waitforstat
mov cx,10000
sub dx,4 ;(22ah)
waitforstat2:
in al,dx
dec cx
je errorstat
cmp al,0aah
jne waitforstat2
mov al,0
ret
errorstat:
mov al,1
ret
ENDP DspReset
;========================
;==- Start Interrupts -==
;========================
;cs:ax=location of interrupt
PROC DoRealint NEAR
pushf ; Push flags
push bx
push cx
push dx
cli ; Disable interrupts
mov dx,ax
mov al,[cs:IrqNumber]
add al,8
cbw ; Convrt byte to word
shl ax,2 ; Shift w/zeros fill
mov bx,ax
push es
sub ax,ax
mov es,ax
mov [es:bx],dx
mov [es:bx+2],cs
pop es
mov cl,[cs:IrqNumber]
mov ah,1
shl ah,cl ; Shift w/zeros fill
not ah
in al,21h ; port 21h, 8259-1 int IMR
and al,ah
out 21h,al ; port 21h, 8259-1 int comands
pop dx
pop cx
pop bx
popf ; Pop flags
sti
ret
ENDP DoRealint
PROC UnDoREALint NEAR
pushf
pusha
cli
mov al,[cs:IrqNumber]
add al,8
cbw
shl ax,2
mov di,ax
push es
sub ax,ax
mov es,ax
mov ax,[WORD LOW cs:OldInt]
mov [es:di],ax
mov ax,[WORD HIGH cs:OldInt]
mov [es:di+2],ax
pop es
mov cl,[cs:IrqNumber] ; (=7)
mov ah,1
shl ah,cl ; Shift w/zeros fill
in al,21h ; port 21h, 8259-1 int IMR
or al,ah
out 21h,al ; port 21h, 8259-1 int comands
popa
popf ; Pop flags
sti
ret
ENDP UnDoREALint
;Figgures the DMA buffer info
PROC CalcForDMA NEAR
pushad
push ds
mov ax,cs
mov ds,ax
mov es,ax
mov [2 + DMA.Next],0 ;assume we do only 1 buffer
movzx eax,[SampleSeg]
movzx edx,[SampleOff]
call MakePage
cmp cx,[SamLength] ;is max less than needed?
jb Skiplengthset ;yes, must do 2 buffers
mov cx,[SamLength]
mov [2 + DMA.NEXT],2
jmp NoMore
Skiplengthset:
mov bx,[SamLength]
sub bx,cx
dec bx
mov [2 + DMA.Length],bx
mov [2 + DMA.Offset],0
mov [2 + DMA.Page],ax
inc [2 + DMA.Page]
NoMore:
mov [DMA.Page],ax
mov [DMA.Offset],dx
dec cx
mov [DMA.Length],cx
pop ds
popad
ret
ENDP CalcForDMA
;input: eax=segment
; edx=offset
;output: ax=page
; dx=offset
; cx=MAX_LENGTH
PROC MakePage NEAR
shl eax,4
add edx,eax ;edx = 32bit absolute address
ror edx,16
mov al,dl ;ax= page
xor ah,ah
ror edx,16
mov cx,dx
neg cx
ret
ENDP MakePage
; returns -1 if load not successful
PROC LoadSample NEAR
pusha
push ds
mov ax,cs
mov ds,ax
mov dx,offset FileName
mov ax,3D00h ;open the file
int 21h
jc @@Error
mov bx,ax
xor dx,dx ;load at offset 0
mov cx,0ffffh ;read in a whole segments worth
mov ds,[cs:SampleSeg]
mov ax,3F00h ; Load in the sample
int 21h
mov [cs:SamLength],ax
mov ax,3E00h ;close the file
int 21h
;now fix the sam so it's playable on a SB
push es
push ds
pop es
mov si,0
mov di,0
mov cx,[cs:SamLength]
cld
FixItLoop:
lodsb
add al,128
stosb
loop FixItLoop
pop es
pop ds
popa
xor ax,ax
ret
@@Error:
pop ds
popa
mov ax,-1
ret
ENDP LoadSample
────────────────────────────────────────────────────────────────────────────
START:
mov bx,ss
add bx,20h ;put sample right after stack
mov [cs:SampleSeg],bx
call LoadSample
call CalcForDMA
call DspReset
mov ah, 256- 1000000/8000 ; 256- 1000000/ HZ
call SetTimeConstant
call TurnOnSpeaker
call StartTransferDMA
mov ah,0
int 16h ;wait for a keypress
call HaltDMA
call UnDoRealInt
call TurnOffSpeaker
call DSPReset
mov ax,4c00h
int 21h
END START
