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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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Thread Tools |
22nd Nov 2022, 8:54 am | #21 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,297
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Re: 6502 NOP generator
I think the zx80 and zx81 had resistors between the ram and the z80 so they could force NOPs into the z80 while the video circuit reads the ram. These would probably prevent any serious bus contention.
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25th Nov 2022, 11:52 am | #22 | |
Octode
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,287
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Re: 6502 NOP generator
Quote:
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25th Nov 2022, 5:58 pm | #23 | |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,297
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Re: 6502 NOP generator
Quote:
He could have disabled the data bus buffers during write but he only uses the read enable to control direction. I wonder how many people built his design and found interupt mode 2 would not work. |
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