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8008guy
January 20th, 2018, 06:08 PM
I just finished testing this tonight. I wire wrapped up a slightly modified IMSAI SIO2 card. I am using a single chip dual baud rate generator. I also simplified the serial output section. I only support RS232 on a DB9. I didn't need SYNC and current loop support. I just finished testing tonight and everything works! Was a fun project.

43144

I used the following code to test the card:





;COMP EQU 083H ; 8251 Command port A
;DATP EQU 082H ; 8251 Data port A

COMP EQU 085H ; 8251 Command port B
DATP EQU 084H ; 8251 Data port B


FP EQU 0FFH ; Front Panel LEDS

ORG 3700H

mvi A, 0H
out COMP
out COMP
out COMP

mvi A, 40H ; RESET 8251
out COMP

mvi A, 04EH ; Set mode to 8N1
out COMP

mvi A, 27H ; Set command Byte TXE,DTR,RXE,RTS = Enable
out COMP

LOOP: in COMP ; Read status bits
ani 02H ; Mask out all but recieve
jz LOOP

in DATP ; Read recieved char
out DATP ; Echo it back out

;in COMP ; Read status bits
;cma
;out FP
;hlt

XMIT: in COMP ; Read status bits
ani 04H ; Mask out all but TxEmpty
jz XMIT ; Jump till bit TxEmpty set

jmp LOOP

glitch
January 21st, 2018, 06:14 AM
Excellent! It's pretty quick/easy to wire up a serial I/O board to emulate many of the popular (and now expensive!) I/O boards. That's part of why I'm working on the reproduction SSM IO-2 boards -- they even have instructions in the manual for how to strap the card up to look like other serial cards.

Always nice to see another hobbyist still using wire wrap :)

8008guy
January 21st, 2018, 07:08 AM
Last year when I was restoring my Altair I bought one of Martin E's serial cards, I've been really happy with that. It made things pretty quick, especially with the monitor he put on the board. Although I felt it was a little like cheating it made it so easy! Around the time I bought Martin's card I was following a few auctions for serial cards on ebay that were just insane... At the end of last year I committed to live the "real" experience and bring the IMSAI up more organically. Now that I have a serial card I'm taking a run at the Tarbell cassette interface. I want to get IMSAI basic up. And then last get CPM running on it. It will be a fun project.

Sign me up for one of your SSM IO-2 boards!!!

I did all the testing on my bench system built around one of Josh Bensadon's 8080 CPU, and of course Don Caprio's front panels. (Which you can see in the pic.) Back in the 70's when I wire wrapped up my 8008 I never would have imagined that I'd still be playing with this hardware 40+ years later and enjoying it so much!

CHeers,

len

8008guy
January 21st, 2018, 08:13 AM
For those of you who might be interested, he is the schematic linked below:

http://www.chronworks.com/IMSAI/IMSAI_SIO2_tmd.pdf

glitch
January 21st, 2018, 09:37 AM
One way or another, there will be Tarbell cassette interface reproduction boards soonish.

8008guy
January 21st, 2018, 09:45 AM
One way or another, there will be Tarbell cassette interface reproduction boards soonish.

Are there any copies of the cassettes (mp3) with IMSAI basic around that are in a Tarbell format?

glitch
January 21st, 2018, 10:09 AM
Not sure, but of course if you have IMSAI BASIC in some other form (I believe it's around out there) you can save it out to cassette once you've got an interface going.

8008guy
January 21st, 2018, 02:30 PM
Not sure, but of course if you have IMSAI BASIC in some other form (I believe it's around out there) you can save it out to cassette once you've got an interface going.

Currently that is what I was thinking, if a copy exists that works too.

Thanks,

len