Using non CMOS eproms on NES Carts

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BokuNES
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Using non CMOS eproms on NES Carts

Post by BokuNES » Wed Sep 30, 2020 8:31 pm

hi to all, well...just whats the title said, it is posible to make nes repros with non cmos eproms, i used a 27128a to make a battle city repro and it didint work, so, its the chips type a problem???

lidnariq
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Re: Using non CMOS eproms on NES Carts

Post by lidnariq » Wed Sep 30, 2020 8:40 pm

No, the NES uses 5VTTL signalling, that should be fine.

If your programmer verifies that you've programmed it correctly, it may be too slow to work in the NES, or you may have a wiring mistake.

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Wed Sep 30, 2020 8:54 pm

lidnariq wrote:
Wed Sep 30, 2020 8:40 pm
No, the NES uses 5VTTL signalling, that should be fine.

If your programmer verifies that you've programmed it correctly, it may be too slow to work in the NES, or you may have a wiring mistake.
i think that maybe is a writing problem, i follow this http://nesdev.com/NES%20EPROM%20Conversions.txt

that link says that for nrom borads there is no lifting pins to make, so, i solder the eprom directly onto the board, maybe thats the problem???

lidnariq
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Re: Using non CMOS eproms on NES Carts

Post by lidnariq » Wed Sep 30, 2020 9:01 pm

What donor PCB are you using?

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Wed Sep 30, 2020 9:03 pm

lidnariq wrote:
Wed Sep 30, 2020 9:01 pm
What donor PCB are you using?
im using a hvc-nrom-03, taked from a tennis famicom cart

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Memblers
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Re: Using non CMOS eproms on NES Carts

Post by Memblers » Wed Sep 30, 2020 9:22 pm

That should be NROM-128, then. Check pins 27 and 1, does the board connect them both to 5V (it should)?

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Wed Sep 30, 2020 9:44 pm

Memblers wrote:
Wed Sep 30, 2020 9:22 pm
That should be NROM-128, then. Check pins 27 and 1, does the board connect them both to 5V (it should)?
both are conected to 5v

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Thu Oct 01, 2020 9:22 am

i tested all point, and all seems to be fine, so i think that the problems are the eproms itself, you cant use non CMOS eproms on the nes alfter all, so, thats all

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Re: Using non CMOS eproms on NES Carts

Post by Quietust » Thu Oct 01, 2020 9:49 am

BokuNES wrote:
Thu Oct 01, 2020 9:22 am
i tested all point, and all seems to be fine, so i think that the problems are the eproms itself, you cant use non CMOS eproms on the nes alfter all, so, thats all
I don't see how an NES cart could possibly fail solely due to using non-CMOS EPROMs - after all, the NES CPU and PPU are themselves non-CMOS!

As lidnariq mentioned earlier, you might need to check that your EPROMs are fast enough for the NES - I believe the PRG ROM needs to be ~250ns (or faster) and the CHR ROM needs to be ~150ns (or faster).
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Jeroen
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Re: Using non CMOS eproms on NES Carts

Post by Jeroen » Thu Oct 01, 2020 10:07 am

Reading the datasheet, it seems the /G enable signal going low is what latches the data out on that particular chip. Make sure your address decoding is connected to that particular pin.

https://futurlec.com/Memory/27128_Datasheet.shtml

edit I checked some pictures of nrom pcbs online: https://www.nintendo8bit.no/famicom/fb_menu.jpg

They seem to be using /E for the enable for the CHR rom. So that would explain why it won't work. Ground /E and connect /G to that pin instead.


edit: talked it over with someone on irc. He thinks that it's not the problem above, however you should tie pin 1 (VPP) and pin 27 (/P) high.

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Tue Oct 06, 2020 9:30 pm

my friends, thanks so much for the info, i will try again tomorrow, i will inform you if this works!, thanks again for the info!

BokuNES
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Re: Using non CMOS eproms on NES Carts

Post by BokuNES » Wed Nov 04, 2020 10:29 am

my friends, sorry for the delay replying this, it works!!!, thank you so much!!!

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