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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Location: St Albans, UK

Re: ZX81 ULA-in-a-CPLD

Post by McKlaud »

No /IORQ, no /NMI ...
Claudius
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Andy Rea
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Joined: Fri May 09, 2008 2:48 pm

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
AFK

overCLK
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Location: Spain

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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Location: Looking forward to summer in Somerset, UK...

Re: ZX81 ULA-in-a-CPLD

Post by 1024MAK »

ZX81 ROM disassembly/ recreated source code available here ;)

Mark

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