Jerry Callen wrote:
> <old fart mode>
My first computer in College was a 32K IBM 7044. This was a single-tasking batch
system. We would place our card decks in a tray where the operators would run them. We
had the largest non-government computer center in the state of Louisiana. After my
tour in Viet Nam, I went to graduate school where the computer center had 1200BPS
terminals to an RCA Spectra 70 (which ran a clone of IBM's DOS). The business school
had its own PDP-8, where I learned assembler. During the summer between terms Iworked
at a bank in Atlanta where we had a 360 processing OCR documents for AT&T. I remember
getting a replacement modem, which was something that had to be brought in on a
two-wheeler.
Going back to the days when I programmed the Burger King POS...
The modem we had in the PDP-8 was made by Novation. No UART. We put the 11 bits into
the accumulator (8 + start + 2 stop bits), and would time the 1200 bits per second by
going into a timing loop. The 8's timing was predicable.
send:
rotate bit into link.
send bit
if acc == 0 return. - I think we had to do a skip on zero followed
by a branch or return.
save acc
load constant for 1200 bps.
tloop:
decrement acc
if non-zero br tloop
load acc
br send
--
Jerry Feldman <[EMAIL PROTECTED]>
Boston Linux and Unix user group
http://www.blu.org
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