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From: bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: XMODEM
Message-ID: <8707200126.AA15199@cogsci.berkeley.edu>
Date: Sun, 19-Jul-87 21:26:43 EDT
Article-I.D.: cogsci.8707200126.AA15199
Posted: Sun Jul 19 21:26:43 1987
Date-Received: Mon, 20-Jul-87 03:46:43 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 26
Summary: act before midnight tonight...

I have several different terminal emulator programs for the Amiga.  All support
XMODEM transfer.  Only one supports XMODEM CRC.  XMODEM CRC is *EASY* to add,
and gives a big reliability boost for transfer over noisy lines.  I'd like to
have this feature on all the programs I use, and to this end I have dug up
the actual specification for XMODEM and XMODEM CRC.  Write to me and ask for
it if you don't already know the formats.

(Send your order before midnight tonight and at no extra charge I'll throw in
source code for not one..., not two..., not even three..., but, yes FOUR
common programming languages!!!! (C, 68000, pascal and 8088))

(I would have done 6502 also, but I doubt it would ever get used... I recall
reading in "The Regional Enquisitor" that all existing 6502 CPUs ceased to
function sometime in late 1986 :-) :-) :-) :-) :-)


(For those of you that don't know, XMODEM uses a single 8 bit exclusive-or'ed
checksum for each 128 byte "packet".   On a noisy line this will often MISS
errors.  XMODEM CRC uses a 16 bit "cyclic redundancy check".  Most of the
extra reliability comes from the larger size of the check value.)

-----------------------------
|\ /|  . Ack! (NAK, EOT, SOH)
{o O} . 
( " )	bryce@cogsci.berkeley.EDU -or- ucbvax!cogsci!bryce
  U	"Success leads to stagnation; stagnation leads to failure."