Erebus.

This is the right place to discuss on how to implement hardware vsync, adding a VIA or AY chipset, puting multiple roms, or how to design a new flash expansion card.
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Silicebit.
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Erebus.

Post by Silicebit. »

@kenneth. A proposal to improve Erebus for future batches :-) . You only need to add a resistor and, of course, modify the PCB.
I/O CONTROL Tristate.
I/O CONTROL Tristate.
Erebusdiagram2.jpg (584.01 KiB) Viewed 724 times
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kenneth
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Re: Erebus.

Post by kenneth »

Indeed, using the three state output coud be a good solution for the open collector problem, it could be added with the reset button update. ;)

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mikeb
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Re: Erebus.

Post by mikeb »

I like that hack :)

It's even better than the diode thing, as it's a proper TTL drive output, either drive the line low, or leave it to float (open).

As noted in another posting, this sort of thing needs to be done on any other thing on the IO control line though (because a.n.other device may drive the line HIGH, while this one pictured is driving LOW, and you still have a conflict).

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Silicebit.
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Re: Erebus.

Post by Silicebit. »

mikeb wrote:
Sat Jun 20, 2020 4:33 pm
... As noted in another posting, this sort of thing needs to be done on any other thing on the IO control line though (because a.n.other device may drive the line HIGH, while this one pictured is driving LOW, and you still have a conflict).
Correct! For this reason I said in the RetroWiki forum, that from now, we all must design the interfaces thinking about a shared bus.
We should to use open collector/drain or Tri-state outputs on /MAP, /ROMDIS, /IRQ, /I/O_CTRL and /RESET lines.
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kenneth
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Re: Erebus.

Post by kenneth »

Silicebit. wrote:
Sat Jun 20, 2020 6:20 pm
mikeb wrote:
Sat Jun 20, 2020 4:33 pm
... As noted in another posting, this sort of thing needs to be done on any other thing on the IO control line though (because a.n.other device may drive the line HIGH, while this one pictured is driving LOW, and you still have a conflict).
Correct! For this reason I said in the RetroWiki forum, that from now, we all must design the interfaces thinking about a shared bus.
We should to use open collector/drain or Tri-state outputs on /MAP, /ROMDIS, /IRQ, /I/O_CTRL and /RESET lines.
We must add the fact that we will also have to choose the interface working area on page 3 and in the ROM area.

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