Cromemco Pri Board and using a non-cromenco centronics printer

[Joe Corda]

Greetings
I've been working on getting a Cromemco PRI board (20-0023 Rev B -see below) to work with a Panasonic KX-P1091i dot matrix printer (which is set to use 7bit ascii data).

Currently I'm thinking my J1 to DB25 centronics pin outs mapping might be incorrect.  Its based on research I did but I'm getting odd output when simply sending A-Z to printer.  
Example:    @@CDDDGHHHKLLLOPPPSTTTWXXX
(See pin map below)

So I have a few questions:

• Does anyone have a "confirmed working" pin mapping for J1 to standard centronics cable?
• Has anyone create a simple db25 to db25 adapter board to put between the J1 and a centronics cable for pin conversion which they can share the gerber files?
• Anyone have documentation concerning pin out for the "Cromemco TRT-CBL" cable mentioned in the manuals?
• Does any one have a simple "tested" 8080 assembly program that just prints the alphabet to a Cromenco PRI J1 port (Just in case I have a coding issue with my test program)

Any help,  guidance or suggestions would be appreciated 
Thanks
Joe

[wpe...@brainless.org]

Hi,

 

Does the board you have 74LS374 ICs or 74LS373 ICs ??? 

 

This is supposed to be the PINOUTs for the 74LS373 board: 

 

J1 Pinout (Port 54h)

 

Pin         Signal  Direction

1             STROBE             OUT

2             DATA0 OUT

3             DATA1 OUT

4             DATA2 OUT

5             DATA3 OUT

6             DATA4 OUT

7             DATA5 OUT

8             DATA6 OUT

9             DATA7 OUT

10          ACK      IN

11          BUSY   IN

12          PAPER END     IN

13          SELECT              IN

14          AUTO FEED     OUT

15          ERROR               IN

16          INIT       OUT

17          SELECT IN        OUT

18-25  GROUND          —

 

 

Software access:

 

Port       Function

54h OUT            write data

54h IN read status

 

 

J2 Pinout (Ports 5A–5C)

 

Pin         Signal  Direction

1             DATA0 OUT

2             DATA1 OUT

3             DATA2 OUT

4             DATA3 OUT

5             DATA4 OUT

6             DATA5 OUT

7             DATA6 OUT

8             DATA7 OUT

9             STROBE             OUT

10          BUSY   IN

11          READY IN

12          RIBBON UP      OUT

13          RIBBON DOWN            OUT

14          CARRIER MOTION      OUT

15-25  GROUND         

 

 

Ports:

 

Port       Function

5A OUT               data

5A IN    status

5B OUT               carrier motion

5C OUT              control strobes

 

 

 

 

 

 

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[Joseph Corda]

Walt
It has 74LS373

The J1 (port 54) pins you supplied seems to  match my example I included

Joe

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[Mike Arnold]

I agree with Walt on the pinout. Note that the TUART and PRI have exactly the same pinout for the parallel port so you can use either in a system. However, there can be confusion about the pinout because Cromemco pin numbers refer to the D25 connector rather than the 26 pin pcb connector. The attached shows both these plus Centronics. If I remember correctly, this cable will work with both CDOS and Cromix although your PRI is not compatible with Cromix (you will need the later PRI with interrupts or a TUART). Happy printing.

[Mike Arnold]

And, if you want to test the port under CDOS then create a text file (text.txt) and send it to the printer port with xfer prt:=text.txt

[Joseph Corda]

Thanks Mike and Walt..
I will review the attached pinout and see what I have incorrect on my setup ...

Joe

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[Chris LaFond]

Joseph:

I was catching up on some emails and saw this message. To run my dot matrix printer from a PRI I had to pull the last bit high or low. I can't remember. Since bit 8 isn't being used, the printer still expects it.

Hope this helps

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[Joseph Corda]

Chris..

Honestly I have not tried yet as the Panasonic KXP-1091i offers a dip switch to set 7 or 8 bit data (though maybe that is not working correctly). 
I will give it a try tomorrow and let you know the results 
Thanks for the suggestion.. 

Joe

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[Bill Mahoney]

Not to throw my $0.02 in here but I did a little table in excel - screen shot attached. Looking at your original description, Joe, it seems like there maybe is a hardware logic issue. The low two bits of the ASCII never come out unless they are both on. Like something is pulling down bits 0 and 1 when it shouldn’t. See my screen shot. You could send it all A’s and look on a scope, then send it all C’s and trace that through, something?

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[Mike Arnold]

Nice one Bill. When I saw Joe's message I did think there might be a pattern there but you seem to have cracked it. Shorts or a faulty driver chip. Or even faulty receiver chip in the printer.

[Joseph Corda]

Bill

Thanks for the observation ..  I did look at that  data but did not make the connection you pointed out ..   I will see if I can setup the scope and run the test you  suggested .  Hopefully track it back to a chip.

Joe 

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[Bill Mahoney]

I’d think that it is maybe as simple as bit 2 is shorted to bit 0 and 1 somewhere along the way.

Glad to help. Putting my grad school credits to use, finally. 

On Mar 17, 2026, at 5:42 PM, Joseph Corda <jjco...@gmail.com> wrote:

Bill

Thanks for the observation ..  I did look at that  data but did not make the connection you pointed out ..   I will see if I can setup the scope and run the test you  suggested .  Hopefully track it back to a chip.

Joe 

On Tue, Mar 17, 2026 at 17:03 Bill Mahoney <bi...@billmahoney.com> wrote:

Not to throw my $0.02 in here but I did a little table in excel - screen shot attached. Looking at your original description, Joe, it seems like there maybe is a hardware logic issue. The low two bits of the ASCII never come out unless they are both on. Like something is pulling down bits 0 and 1 when it shouldn’t. See my screen shot. You could send it all A’s and look on a scope, then send it all C’s and trace that through, something?

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CAACXqMcJ6Upy5ebDgzTkOB5ki0aBzGjh41yearfmUSx5ferbMw%40mail.gmail.com.