You don't need to delay it, not unless you're using a booster to speed up ROM ( but that can be fixed in the booster anyway) , as the CPU will not pick up the data for 100+ns anyway.
Smonson's slow H4 build
Re: Smonson's slow H4 build
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Re: Smonson's slow H4 build
What about /OE though? Just tie it to ground?
Yes, I believe so. That part is from the schematic provided by the original author (Ted Rossin). By ROM_OE, do you mean LDS/UDS?
Re: Smonson's slow H4 build
You can tie CE to GND.. OE is used to enable the ROM.. then put a diode to The same signal with a diode then you can pull DTACK low as well.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
- stephen_usher
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Re: Smonson's slow H4 build
I used the GAL to do the address decoding, which controls /OE and the /AS line to run /CE on the ROM. (This matches the timing diagram as /CE should be before /OE.) This meant that the ROM was primed to output whenever an address appeared on the bus. It was then up to the GAL to decode the address or /ROM2 along with /RW to determine if it's a read operation so as to enable the output from the ROM (/ROE in my schematic). This same signal was used to enable /DTACK via the 74LS244.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Re: Smonson's slow H4 build
I could go down the custom route using a cheap CPLD, but using "F" high-speed logic seemed a lot more bullet-proof. I also can't stand soldering the EQFP packages on MAX Vsstephen_usher wrote: ↑Fri Mar 26, 2021 12:40 pm
I used the GAL to do the address decoding, which controls /OE and the /AS line to run /CE on the ROM. (This matches the timing diagram as /CE should be before /OE.) This meant that the ROM was primed to output whenever an address appeared on the bus. It was then up to the GAL to decode the address or /ROM2 along with /RW to determine if it's a read operation so as to enable the output from the ROM (/ROE in my schematic). This same signal was used to enable /DTACK via the 74LS244.
Re: Smonson's slow H4 build
Yep!
But CE should be OE on the diode signal
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Re: Smonson's slow H4 build
For this particular application, I really would suggest using slower LS types... With them being lower power and slower they are a lot less "noisy".
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.