Date   : Fri, 02 May 1986 03:06:09 GMT
From   : The Wumpus <aptr%ur-tut.uucp@BRL.ARPA>
Subject: Re: Programming a Xerox 820-II

In article <388@brl-smoke.ARPA> YOUNG@dec-marlboro.ARPA writes:
>I have an old XEROX 820-II which I am using for packet radio purposes.
>I would like to use DTR/DTS on the serial port.  I'd
>prefer to do it in TURBO Pascal, but assembler is acceptable.  Can
>someone tell me how to do this (or does someone have a code fragment
>I can look at)?
>

Forgive me for posting this respons, but our mailer (conservatively)
stinks...  You know something is wrong when it is easier to send from
BITNET to UUCP then from UUCP to UUCP.


Well, you come to the right place...

First question:   Which I/O port(s)?   There are several usable I/O ports
including 2 serial and 2 parrellel.   (not to ntion the I/O bus)  If you
are really deperate, and can trash the disk drives (ie. go super-dedicated
and burn PROMs) you can use two more parrellel ports that the Disk Drive
Controller uses.  (I don't really recommend this approach.)

For using the DTR/DTS on the serial ports, those lines can be hardware
jumpered to do either function to allow both port to be used for DTE and/or
DCE equipment.  The information on how to change the settings is in the
book mentioned below.  Access to them is actually best left to going
through CP/m since it is easier then using assembly routines.  You can
you BOIS calls to do the communication, or even output to the serial
ports from the ports on the z80.  Again, more information is 
available in the book.

As to where to get information about them.   Xerox publishes (or atleast 
used to) the "Xerox 16/8 PC Technical Refrence Manual".  It isshould be
available from your nearest service center.   Don't be scared off because
it says "16/8" instead of "820-II" because they are the same machine,
except for the addition of a seperate 8086 processor board in the expansion
bus on the "16/8".   Everything in the manual that doesn't concern the
8086 dual-processor is valid for the 820-II.

If you have any other questions about the 820-II, send me e-mail.  I have
two of them in my basement at home.

The Wumpus     UUCP:   allegra!rochester!ur-tut!aptr
               BITNET: aptrccss@uorvm