The intelligent file transfer protocol is a means of reliably exchanging binary files used by Amstrad computers. It is used by the PCW program MAIL232 (transfer 'as HEX') and, I believe, by various CPC programs. This description comes from Amstrad's CPS8256 interface manual, and is copyright © Amstrad.
The protocol for the intelligent file transfer is as follows:
(For your reference)
STX = [CTRL]B = ASCII 2
ETX = [CTRL]C = ASCII 3
ACK = [CTRL]F = ASCII 6
NAK = [CTRL]U = ASCII 21
Additional notes (not from the manual): 2-byte words are transmitted in little-endian format, i.e., least significant byte first. The filename format is as follows:
0 1 byte drive: single upper-case letter or '@' to indicate default drive 1 11 bytes 8-byte filename and 3-byte extension in upper-case (no dot) 12 4 bytes four NULs (0x0)
(subject to confirmation)
A CP/M program from the same manual to transmit a file using this protocol on AUX: can be downloaded as HEX format or as a CP/M executable. Syntax: IFT FILE.TYP.