ZX81 ULA-in-a-CPLD

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
McKlaud
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Re: ZX81 ULA-in-a-CPLD

Post by McKlaud »

No /IORQ, no /NMI ...
Claudius
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Andy Rea
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Re: ZX81 ULA-in-a-CPLD

Post by Andy Rea »

what i wanna know is what the heck is the ~IORQ line doing after the nmi stops... what in the world would cause so many io instructions ?

how many lines has your logic analyser got ? i'm thinking about probing the entire data bus and ~m1 in addition to the other lines then you can decode the exact instruction prior to a failure

Andy
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overCLK
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Re: ZX81 ULA-in-a-CPLD

Post by overCLK »

Andy Rea wrote: Sat Nov 10, 2018 9:23 pm what i wanna know is what the heck is the ~IORQ line doing after the nmi stops... what in the world would cause so many io instructions ?

how many lines has your logic analyser got ? i'm thinking about probing the entire data bus and ~m1 in addition to the other lines then you can decode the exact instruction prior to a failure
Only eight. :-(
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1024MAK
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Re: ZX81 ULA-in-a-CPLD

Post by 1024MAK »

ZX81 ROM disassembly/ recreated source code available here ;)

Mark
AndyP
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Re: ZX81 ULA-in-a-CPLD

Post by AndyP »

I realise that this is a very old thread but, does anyone have any gerbers/schematics/pcbs/ lying around for any of the ULA replacements that use either Xilinx or Altera devices?

Thanks

AndyP
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1024MAK
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Re: ZX81 ULA-in-a-CPLD

Post by 1024MAK »

Have a read of this topic for all the publicly available information.

The ‘internal’ details of the other CPLD ULA versions are not publicly available as far as I know.

Mark
AndyP
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Re: ZX81 ULA-in-a-CPLD

Post by AndyP »

Hi Mark,

Thanks, I'd already found them but was trying to be a lazy b*gg*r and not have to design my own pcb.

Not to worry, time to get Kicad updated once I've mastered CPLD design.

AndyP
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