Page 1 of 1

Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 9:16 am
by zlakomanoff
Hello everyone.

I was made custom game cartrige, with micro mages game, based on original "F1 Race" famicom cartrige

Image

Image

Image

when i run this cart on dandy famiclone, game working fine

Image

Image

but when i run on original hardware, i got this

Image

Image

game and music work fine, all sprites shown as "nine" digit,
are anyone known whats can be wrong ?

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 9:32 am
by lidnariq
Check what CHR's /OE and /CE signals are connected to. I'd hunch you've accidentally left it enabled all the time, and that interferes with the real PPU's multiplexed address/data bus. (Many famiclones demultiplexed this bus)

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 9:50 am
by zlakomanoff
lidnariq wrote:Check what CHR's /OE and /CE signals are connected to. I'd hunch you've accidentally left it enabled all the time, and that interferes with the real PPU's multiplexed address/data bus. (Many famiclones demultiplexed this bus)
CE connected to the GND, OE connected to 17 pin (PPU /RD)

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 10:14 am
by lidnariq
CHR /CE should be connected to PPU A13. /OE is correct.

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 11:57 am
by zlakomanoff
lidnariq wrote:CHR /CE should be connected to PPU A13. /OE is correct.
Yes, /CE connect to the PPU A13, looks better but something wrong
also i connect CHR EEPROM A13 to GND - game run perfect!

Thank you "lidnariq" !

Where i can read about PPU A13 behaiour ?

Image

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 12:26 pm
by lidnariq
... mayyyybe nesdevwiki:Cartridge connector ?
Most boards tie [PPU A13] directly to the /CE of CHR ROM or CHR RAM to map it into pattern table space ($0000-$1FFF) without any extra logic.
Or maybe nesdevwiki:PPU memory map?

Re: Twin famicom ppu glitches

Posted: Thu Jul 11, 2019 12:29 pm
by NewRisingSun
I did not know that even the Dendy Junior could already deglitch the PPU signals! I thought only later famiclones could do that, because I have only seen post-2000 cartridges that require such a thing.