CHR$X16

ZX80 / ZX81 hardware and software requested for either sale or swapping
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roganjosh
Posts: 20
Joined: Thu Jun 14, 2018 12:59 pm

CHR$X16

Post by roganjosh »

My recent query, regarding anyone with a UDG4ZXPAND they wanted to sell, understandably fell on stony ground. That being the case I'm wondering if anyone on this forum ever produced a PCB for the CHR$X16. If so, and if they have a spare one for sale (or the equivalent Eagle/KiCad/Designspark/etc files), I'd be happy to hear from them.

Alan
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mrtinb
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Re: CHR$X16

Post by mrtinb »

If you wan't an interface for User Defined Characters (UDG), there is also the Chroma interface, which supports color and scart video output on top of that.

Unfortunately it's also sold out at the moment. :(
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
Mustermann
Posts: 37
Joined: Sun Dec 22, 2019 12:09 pm
Location: Augsburg, Germany

Re: CHR$X16

Post by Mustermann »

I was able to build an internal CHR$16 / CHR$128 mod.
There is no PCB, just soldered a RAM on the back of the ROM and build a small dot pcb.

https://sinclairzxworld.com/viewtopic.p ... 302#p37302
This need at least 8-16k range not used by external RAM.

I can tell in more detail if needed.

I also have a rough idea what UDG4ZXPAND is doing. I assume it is possible to build that function with standard parts as well.

Regards,

Max
ZX81 issue 1 near to original state
ZX81 issue 1 56k internal ram with battery backup, UDG, CHR$128 and WRX enabled
Minstrel 3 ZX81 clone 64k with battery backup, UDG, CHR$128 and WRX enabled
roganjosh
Posts: 20
Joined: Thu Jun 14, 2018 12:59 pm

Re: CHR$X16

Post by roganjosh »

Thanks Martin. I'd noticed that and am on the waiting list for one. Immediately available UDG interfaces are more rare than Hen's teeth....

.. and thanks Max too.
I had read the posting you linked to. An admirably devious solution. Although I'm not averse in principle to soldering other components to IC pins on mobos that's so far been limited to getting base hardware working properly (e.g. spider mods, resistor arrays to Atari DMA chips, etc). Piggybacking a RAM on a ROM chip felt a step too far at this stage. It may be something to consider if I get yet another ZX81. It would be interesting to know what the FPGA (I assume there's one from one of Andy Rea's postings) is doing in detail but emulating it using standard chips, though a very fascinating intellectual exercise, would be overkill just for my case.

Fortunately UDG development under EightyOne can proceed apace. I'm also dipping into DesignSpark in idle moments for this circuit http://www.user.dccnet.com/wrigter/inde ... CHR$X4.htm
but under the circumstances that's out of interest rather than necessity. I could see it getting occasional use.

Alan
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