Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ames!pacbell!sactoh0!ianj
From: ianj@sactoh0 (Ian R. Justman)
Newsgroups: comp.sys.apple
Subject: Interrupt handling with a modem in CP/M
Message-ID: <1622@sactoh0>
Date: 18 Jul 89 08:57:32 GMT
Organization: SAC-UNIX (Public Access), Sacramento, Ca.
Lines: 25

I need some help with writing a driver for a communications program
when using CP/M.  (I know, I know!  I'm using an archaic operating
system, but this archaic OS does a lot of things I need it to do!)
I have an Apple ][ Plus with 64k, a Microsoft SoftCard clone, a
Videx Videoterm, and a Super Serial Card driving the modem.  I
wrote an interrupt handling routine which is activated when a
character comes in and shoves the character into a circular buffer
within the driver space (it is 256 characters long, BTW...).  Even
with that in place, I still lose characters when a remote system
(say for instance, this Unix system I'm calling (I'm calling on
another computer in the house)) clears my local screen when at
1200, but I scroll ok.  However, at 2400 baud, I loose characters
during scrolling.  The actual character read occurs only during the
interrupt routine and the programs read-a-character instead of
reading the ACIA's data port, it reads what's in memory denoted by
a memory location stored in one of the Z80's register pairs
adjusted with a pointer in the Z80's base page.  I'm at a loss.
Can someone please help?

Thanks in advance.
-- 
Home:   Ian Justman       |UUCP:                 |"One of the few
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