Date : Mon, 22 Oct 1990 09:34:31 GMT
From : zephyr.ens.tek.com!tektronix!nosun!techbook!fzsitvay@beaver.cs.washington.edu (Frank Zsitvay)
Subject: Is this a Xerox 820 micro? If so, now what?
In article <2499@ux.acs.umn.edu> hughes@ux.acs.umn.edu (Steve Hughes) writes:
>
>
>Okay, here's a hardware ID challenge:
>In the hopes of saving a few buck$ and putting off
>buying a computer of my own (I program at work on a IIci,
>getting a machine I can actually afford would be just to pitiful),
>I have bought a cheap terminal from a local surplus shop.
>I wanted to get something to dial up the mainframe with, using my
>old 1200 baud modem that has been idle since I sold my IIe.
>They had lotz of Adm3as and a few CDC and a couple of Hazeltine
>1420's, (none of which worked) all for $39. After screwing around with
>what they had for a couple of hours, I settled for an
>unidentifiable Xerox terminal that had a solid looking screen and
>a very nice detatched keyboard. I was able to get it to work well
>with an old 300 baud modem in the shop, so I figured I'd give this one a shot.
good choice thus far... broken terms are a waste of time...
Before i go on, this followup is contigent on Beaverton Telephone
throwing me a bunch of line noise that just might disconnect me. It makes
vi a bitch to use...
>
>Now here is the deal: No documentation, and despite my best
>efforts, I cannot make it work at higher than 300 baud! Not with my
>(admittedly ancient, Novation Auto-Cat 212) modem or with a direct
>connect to an IBX box (on campus) capable of up to 9600 baud. This is
>nuts; it was built in 1984, it simply MUST be capable of faster
>operation, and I am hoping that someone reading this knows
>about this machine and can help me out.
it is. baud rate generator is located at port 00H, write only.
you can write to this with the monitor, using the "o" command. syntax
is o port, data . all values must be entered in hex.
Baud rate table
00 = 50 baud
01 = 75 baud
02 = 110 baud
03 = 134.5 baud (very odd)
04 = 150 baud
05 = 300 baud
06 = 600 baud
07 = 1200 baud
08 = 1800 baud
09 = 2000 baud
0A = 2400 baud
0B = 3600 baud
0C = 4800 baud
0D = 7200 baud
0E = 9600 baud
0F = 19.2 Kbaud
>
>Here is as much as I know about it:
>ABSOLUTELY NO DIP SWITCHES.
>Product Code (from bottom of monitor unit): UO5.
>Description: Monitor is green filter over a white phosphorous crt,
>detatched keyboard, keyboard has numeric keypad on the right side,
>"Xerox" nameplate in upper left corner of keyboard unit. "Help"
>key in upper left corner of keyboard (where you might expect to find "esc").
From the sounds of it, you have an 820 - II .
>
>There is a COMM port, Printer Port (RS-232) and for God's sake,
>a DISK DRIVES port and a reset button on the back of the unit.
>I open the case to check things out: I find a Z-80 MPU.
>The machine starts up with a beep and displays the following message:
>
>Xerox v 4.04 C 1982 Xerox Corp.
>
> L - Load System
> H - Host Terminal
> T - Typewriter
>
>m
>0000 00 <-stops here and waits for me to type a hex digit, then
> continues
that command allows you to enter a specified value into any memory
location. if your monitor doesn't support the o command, you will need
to enter the instructions to change baud rate into memory, and use the
goto command to execute it.
perhaps the baud command would work if you entered just the b.
>
>Seems like I should be able to replay my session, scroll up and
>down, etc., but God (and Xerox) only knows how. Despite the Copyright
>dates, the machine has stamped on the bottom of the monitor unit
>"Manufactured Sept 1984." Opening the case shows a Z-80 board with
>all kinds of jumpers, pins and ROM chips with "v 4.04" printed on their
>labels. Also one card plugged into an edge connector.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
That's the givaway that it's not an 820 - I. i wish i could help
you more, but the only info i have is for the -I machines, and your machine
is mostly likely a -II. the baud rate generators are the same in each
machine, so you should be able to use the table above to select baud rates.
your best bet would be to find someone with a similar machine, get some
disk drives and make a boot disk. run cp/m and use a terminal emulator.
by the way, the 820 machines emulate an adm 3a directly.
>
>Since this is a Z-80 machine, it must have run CP/M, and I have
>recently heard that it may in fact be a Xerox 820 microcomputer.
>If this is so, I would be very interested in buying a copy
>of the users manual from someone. I don't think I would be
>interested in disk drives, etc, but I would be intersted in
>discovering if the ROM host terminal mode supports some kind
>of terminal emulation, or if it will allow me to set parity, stop
>bits, etc..
It's really a fine cp/m machine. although it probably has seen its
better days, using it as merely a dumb terminal is a waste of resources.
Find some disk drives (i think it can handle both 8 inch and 5 inch,
check the controller chip. if it's a 1771, your stuck at single density
and (practically) 8 inch drives, if it's a 179x you can use either.)
and enjoy the machine for what it is.
they work great as a bbs host... :)
--
fzsitvay@techbook.COM - but don't quote me on that....
American Oil Company motto - Bend over, We'll pump!!!