Xmodem

[Alex Freed <alex_news@alexfreed.com>]

Thanks for all the pointers. Unfortunately the comm packages were a bit 
too heavy to my taste and I preferred serial over audio in this case.

A little bit of googling found this:

http://www.findthatdoc.com/search-17180267-hDOC/download-documents-xmodem-receive.txt.htm

The small assembly program to receive data via Xmodem CRC.
I only had to replace a few addressed - ACIA registers and zero page 
locations. Assembled with ACME and it works. Only 1 K of code. Exactly 
what I wanted.

-Alex.