Help for Xmodem

Xmodem is often called the "lowest common denominator" protocol, and
is the father protocol of many others. Xmodem sends files in blocks
of 128 characters at a time. When the receiving computer is
satisfied that the block has arrived intact, it signals so and waits
for the next block. Error checking is a checksum or a more
sophisticated Cyclic Redundancy Check. Telix supports both and will
automatically use the right one. During a download, Telix will
attempt to use the CRC, but will switch to checksum if it seems the
host does not support CRC. The Xmodem protocol also needs a setup of
no parity, 8 data bits, and 1 stop bit. If your communications
parameters are different from these when you start an Xmodem
transfer, Telix will switch to the required setup for the transfer,
and back to the original setup after it is finished.

Because of the need to wait for acknowledgement after each block,
Xmodem is capable of approximately half the maximum theoretical
transfer rate.