Date   : Wed, 28 Jun 1989 16:05:00 EDT
From   : GHK%NCCIBM1.BITNET@CORNELLC.cit.cornell.edu
Subject: Buffering with Softcard CP/M and Super Serial Card on Apple II

> Date: 24 Jun 89 09:50:42 GMT
> From: pacbell!sactoh0!ianj@ames.arc.nasa.gov  (Ian R. Justman)
> Subject: Buffering with Softcard CP/M and Super Serial Card on Apple II
>
> I have a problem using some of my communications software on my
> Apple II Plus using Softcard CP/M and a Super Serial Card clone.  I
> keep losing characters like crazy.  Is there a way to buffer
> incoming characters so I don't miss a beat?  Thanks in advance.

Due to the slow clock speeds of the 6502, which does all of the I/O
for the PCPI APPLICARD, it is very capable of loosing characters.

Functions such as ringing the bell or clearing the screen takes all
of the 6502 and any further characters being recieved will be trashed
until the current process is complete.  The only way to avoid this
is to allow the board to generate a processor interupt and store the
data in a buffer until there is time to do something with it.  This
works well but you will probably have to write it yourself.  This is
not an easy task without the PCPI developers kit.  The interupt must be
written in 6502 native code and interfaced with the PCPI BIOS.  The
developers kit has the tools needed for this process.  I wrote a versio
for the Promethieus Versacard and was very succesful in getting it to
work for speeds up to 19200 bps.

       Gary Hutchison
       GHK@NCCIBM1