PCW serial port design

Started by JonB, 12:20, 10 September 18

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Those of you who have a uIDE (or have read the Wiki page I wrote about it) might have noticed that I planned to build a Z80 bus board and CPS8256 serial / parallel port clone that connects to the Z80 bus. This card would be plug and play as the driver is already built into CP/M Plus. It's for 8000 series machines only (for some reason my CPS8256 doesn't work on the 9000 series machines).

There was zero interest expressed in either of these two boards. Except, now I have one message from someone who is interested in the serial board design, but it is far too expensive to prototype and build for just one person. I've written this post to ask if anyone else is interested?

To connect it to the PCW you would need a Z80 shim or an expansion port adapter. If you already use a uIDE all you need to do is fit a second 40 way socket to your Z80 bus cable, and you should be able to just plug the CPS8356 clone board into it. On the other end (serial/parallel) it currently has a pair of headers such as you'd find on a PC motherboard; the idea was to use a PC serial / parallel socket back plate to connect it to the serial line and printer as pictured below, but I need to verify I have all the pins on the board the right way round.

I would offer it along the same lines as a uIDE (bare board or fully populated) but it's likely to be expensive fully built as it's much more complicated than the uIDE and so there are more parts and labour required to build.

Anyway, if you want to see this board become a reality, please let me know.

Thanks all




Thanks Jon,

Was this discussed before?   My problem is that I have a CPS8256 unit, that works OK, only I don't have a connector for it.   Well, I do, but it's in use for the uIDE, and the latter is FAR more use than the CPS.   Usually.   Not a big deal, I guess, to just swap them over if ever I really NEED the CPS.

Another thing is that my CPS has the SCA (?) mod for a RTC, although I'm not sure about the state of the battery now.   Last time I used it, it still worked, but the battery did not keep the clock going for too long.   Maybe just needs a good charge up?

What WOULD be useful, of course, wound be a connector for the uIDE cable that I could just plug the CPS onto.   Would that be possible?   Of course, I understand that that would be no help regarding your new project!!

Best of luck.



You'd need a PCW expansion port connector with multiple edge connectors coming off it, sort of like a backplane. Problem is, the design of the PCW add-ons makes it hard to do this. They have their connectors perpendicular to, and in the middle of the PCB rather than at the edge. A PCW backplane can be made (there was a series of magazine articles that showed you how) but I don't think you could plug any of the standard cards into it due to the type and orientation of their connectors.

If you want to use the CPS with uIDE you should use a Z80 shim to connect uIDE to your PCW's Z80 socket, freeing the expansion port.

The Z80 bus/backplane design is a sort of cut down version of this idea. It's meant to allow you to plug a uIDE into it and other cards like the serial card or dk'tronics sound card clone (which I might have a go at). I think it needs to be extended though, to carry the other PCW control signals that are on the edge connector. This would be do-able because the uIDE PCW expansion port adapters all expose the lines as a row of jumpers, so you could connect those to the Z80 backplane with a separate ribbon connector. Thus, any cards requiring the additional lines that are sitting on the bus can access them. A good example of such a card is the one I'd need to build to enable booting direct from the uIDE... if I were to build such a card..


For the uIDE I use a Z80 shim, but I'm still interested in a multiple expansion port, for my CPS8256 and the dk'Tronics joystick and sound adapter.

Best regards,


Maybe an Mother X4 is needed for the PCW.  ;)
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Quote from: GUNHED on 14:55, 11 September 18
Maybe an Mother X4 is needed for the PCW.  ;)

If someone develops a "Mother X4" for the PCW, Centronics ports should be provided for the German extensions besides EDGE.


MotherX4 bus boards can be plugged into the PCW's expansion port as-is. All it does is connect 4 male IDC sockets to the port, in parallel as far as I can see.

However, as the pinout of the PCW and 6128 expansion ports are different, any card currently designed to be used with MotherX4 will not work when connected to the PCW. With one exception, and that is the uIDE PCW expansion port adapter (modified with a 50 way IDC socket instead of an edge connector) / uIDE combination.

Producing MotherX4 boards for the PCW is straightforward, but not cheap, as the boards are relatively large and have all these 50 way IDC connectors on them. For example, when researching the Z80 bus board I found it difficult to source PCB mounted female IDC 40 way plugs at a decent price. The bus card has 5 slots plus an "input" slot to connect via a ribbon cable to the Z80 shim or PCW expansion port bus adapter, but as already noted, it does not support the PCW specific signals that are present at the expansion port connector.

The Z80 bus board does give one additional feature though, and that is the facility to add an external power supply to drive boards connected to it. You'd use this if you found the PCW's PSU was being overtaxed by the cards plugged into the bus.


Quote from: sucram on 17:10, 11 September 18
If someone develops a "Mother X4" for the PCW, Centronics ports should be provided for the German extensions besides EDGE.

I don't understand this. Do you mean you want to provide a bus for the Centronics port as well? Is it standard on the German Schneider PCW?

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