Mr-X Soundcard

[mahjongg]

yeah, I should have simply listed them, note that the original ZON X-81 also accepted addresses with A4 = 0.

perhaps I should change the schematic so that the A4 input to the triple and port can be jumpered to either be A4 or simply as high.

[mahjongg]

well, here is version 2.0 with some corrections and improvements:


the red text should actually start with: "a low on any of the address lines..."
on a ZX81 external I/O is selected by making one address of the eight low, while keeping the others high, (And doing an I/O read or write). The spectrum used the exact same selection method, but added a fifth address line that could be low. If all these dresses are high during an I/O then the PSG may (and will) be selected.
Note that for the purpose of the ZON X, the expansion port is a subset of the Spectrum's expansion port, so a ZON X could be plugged into the spectrums expansion port, and work with addresses with A4 being high (so as not to select other internal, or looped through peripherals).

I now have explicitly listed the adresses the ZON X (and XON X-81) "listened to".

note I corrected the notation for the BDIR and BC1 bits, as the first schematic still used the low level logic notation of my own PSG for the ZX81+35 schematic, which isn't valid here.

note that any modern application would probably use 74HCT11 and 74HCT02 logic, and half a 74HCT74 for the divide by two divider. especially the 7472 is very ancient indeed.

if you see any errors, or if you have any comments, please do not hesitate to contribute!

[mahjongg]

Well, hopefully this should be the final version (revision 2.1)

ZON X-81 RE-CREATED SCHEMATIC.png

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[mahjongg]

Started a project at RevSpace about my own soundcard for the ZX81+35.
https://revspace.nl/Zon_X-81_expansion_for_ZX81%2B35

[mahjongg]

This is my version for the ZX81+35, in development.

PSG_for_ZX81+35_REV_1.1.png

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Worked out the logic for also reading PSG registers, now attempting to minimize the logic.
If you are wondering why there are three interface connectors drawn, one is for the female pin header for connecting to this board, another is for the edge connector making the ZX81+35 compatible with other peripherals for the ZX-81 (like the printer), and the third is if you want to forgo the edge connector, and use a pinheader like the ZX-81+35 instead (Will see if its possible in the layout to combine edge connector, and optional pinheader).

[mahjongg]

Further design implementations of the ZON-X compatible PSG for my clone the ZX81+35 you can find in my main ZX81+35 thread.

[mahjongg]

after a long layout session on the ZX81+35, with which I corrected an error in the expansion port layout I have continued with the schematic and layout of the PSG expansion board for my ZX81 clone:
this is the current schematic:

PSG_for_ZX81+35_REV_2.0.png

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[mahjongg]

Here is the finished and optimized PCB Layout of the PSG expansion board for my ZX81+35:

Layout sound expansion.PNG

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[mahjongg]

updated the above picture.

[Fwapp]

Is the Mr X soundcard still available?

I'd love to be able to get hold of one.