New hardware I/O board using Parallax Propeller

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
tdg8934
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Re: New hardware I/O board using Parallax Propeller

Post by tdg8934 » Thu Jun 13, 2019 9:45 am

Thanks Bean. Yes I have had many propeller cards over the years. I just haven’t played with one in a couple of years. I’m pretty familiar with Spin but only mildly familiar with Propeller ASM.

Bean
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Re: New hardware I/O board using Parallax Propeller

Post by Bean » Thu Jun 13, 2019 1:48 pm

I've decided to put the 16K of RAM on my board also.
Can someone explain what I have to do so that it support true Hi-Res mode ?
And maybe why it needs to be done ?

Thanks,
Bean

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1024MAK
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Re: New hardware I/O board using Parallax Propeller

Post by 1024MAK » Fri Jun 14, 2019 12:26 pm

Wilf goes into considerable detail about the ZX81 video system here ;-)

Yes, we know that the pages are full of ? symbols (discussed on here a while ago).

In order for RAM to be hi-res capable, it must output data during both the Z80 read cycle and during the Z80 refresh cycle. So when either /RD is low or when /RFSH is low.

Does that help?

Mark

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