Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!ucla-cs!zen!ucbvax!hplabs!hpcea!hpfcdc!hpfcdq!vodall
From: vodall@hpfcdq.HP.COM (Bill Vodall)
Newsgroups: comp.sys.m6809
Subject: Re: Caching (was: 512K RAM upgrades)
Message-ID: <300004@hpfcdq.HP.COM>
Date: Tue, 18-Aug-87 16:10:03 EDT
Article-I.D.: hpfcdq.300004
Posted: Tue Aug 18 16:10:03 1987
Date-Received: Sat, 22-Aug-87 19:19:09 EDT
References: <1987Aug11.203541.6684@chp.uucp>
Organization: Hewlett Packard, TWO
Lines: 39


> I'm running around now trying to find R.S. stores that still have a
> RS232 pak or two lying around.  I want to get 2-3 more!

The RS232 pak on a coco II with a ram disc makes a "real" system.  I liked
it so much that I did go out and get another RS232 pak.  But, the killer
is that only 1 pak at a time will work as an interrupt driven device.  This
is because the 6809 int line doesn't go to the multipak.  The pseudo int
line from the multipak goes to one of the control inputs on a 6821.  The
RS232 driver recognizes the int from the 6821 when the rs232 pak changes
the state of the control line.  The multipak hardware selects one of the
4 paks interrupt lines to connect to the 6821 so only one device at a
time can be active.  I shorted the int line on both slots 0 and 1 but that
still didn't work.  One RS232 causes an interrupt but the other is checked
and the system hangs solid.

There are some workarounds:

  Use the virtual interrupt driver supplied by Tandy. This gives you 300 baud
  and doesn't work much better than the bit-banger port.

  I've used the second pak just by writing a basic routine to check the state
  of the ready bit.  It works at 1200 baud but it's not near the solution I
  want for an OS9 system.

  My future plans for the second port consist of furthering my modification to
  the hardware by running the int lines of paks 0 and 1 on the multipak to the
  real interrupt line inside the coco.  Then I'll finish modifying the
  acia driver to use the real interrupt instead of messing with the 6821.
  In addition to 2 real RS232 ports I'll now be able to use the multipak
  interrupt for the speech pak.  With the additional two 6850 acia's I've
  added this'll give me 4 serial ports on the coco.

  I plan to use the coco on the modem, packet radio tnc, real 80x24 terminal
  (Heath Z89) and laptop simultaneously.  The only problem is that I can't
  put the cover on anymore.  Too many wires sticking out.


Bill Vodall