9 Jan
2001
9 Jan
'01
3:01 p.m.
On Jan 9, 18:35, Tony Duell wrote:
I have a reasonable set of IBM Techrefs, and the
timing for the 'IBM
Graphics Printer' (a rebadged Epson MX80 or something like that) is much
the same. In fact that's what I used as the 'standard' to design my
interface. Of course what I'll discover too late is that the Epson timing
(or that of other common printers like the Deskjet family) didn't
actually have to be anything like that and that the authors of various
OSes did something totally different that worked with common printers...
FWIW, the two assembly-language routines I can think of that used 7-bit
ASCII (one on a Z80 and one on a 6502) both did it by waiting for BUSY to
go false, then wrote (char AND 7FH) to the port, wrote (char OR 80H), wrote
(char AND 7FH) again, and exited. The eighth data bit was inverted and
used as the strobe.
--
Pete Peter Turnbull
Network Manager
Dept. of Computer Science
University of York