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From: gord@spycal.UUCP (Gord Delaney)
Newsgroups: comp.sys.amiga
Subject: Questions on Parallel Port
Message-ID: <157@spycal.UUCP>
Date: Tue, 14-Apr-87 17:39:34 EST
Article-I.D.: spycal.157
Posted: Tue Apr 14 17:39:34 1987
Date-Received: Sat, 25-Apr-87 19:14:58 EST
Organization: UNISYS, Calgary, Alberta
Lines: 35

I am attempting to connect my AMIGA to another system (an 8085/88 S100)
via the parallel port.  After building a bi-directional parallel port
for the S100 (from a 8255), and getting some software running on both
sides, I have finally managed to transfer data without error in both
directions.

Now, to my problem. The data transfer rate that I'm seeing is less than
6 Kbytes/sec. Actually, it is 170 microsec per byte.  I was anticipating
something in the 20-30 microsec/byte (40 Kbs) range.  When I was doing
the original work on the S100, I was using an 'interrupt mode' for my
software, but found that 1 pass through my 'very tight' interrupt code
took around 120 microsec.  I have since re-designed the S100 software to
use a 'polled' mode and now the 'Data Ack' is returned within 15 microsec
of the request.  I now believe that the pathetically low transfer rate is
because I am using the "par.device" driver on the AMIGA which I assume is
working in an 'interrupt mode'.

Now, to my questions:
  - Does anyone know of a way to speed up the "par.device" driver?
  - Is there a way that I can access the 8520 directly AND still be a
    "well behaved task"?  In my hardware manual (the original CBM version),
    in appendix E (or maybe F), a description of the 8520 is given.
    However, very little is mentioned about the 'FLAG' and 'PC' pins.
    Can I disable the 'FLAG' interrupt and read the status of the 'FLAG'
    pin directly?  The 'PC' output looks like it takes care of itself.

Thanks in advance for any help, and to all those who have made this group
such a valuable resource for AMIGA users.


-- 
        Gord Delaney - UNISYS (SPERRY) Calgary, Alberta, Canada

        UUCP:  ...ihnp4!alberta!calgary!spycal!gord
.