lidnariq wrote:
You will need to disable the following signals for any disabled slot:
CPU M2 (tied low for cart)
CPU /ROMSEL (tied high for cart)
CPU /IRQ (high impedence)
PPU /RD (tied high)
PPU /WR (tied high)
CIRAM /CE (tied high)
CIRAM A10 (high impedence)
You CANNOT skip any of the above, otherwise some games WILL conflict.
You may also want to tie
CPU A14 (low)
PPU A13 (high)
PPU /A13 (high)
Be careful, hotplugging a cartridge, even given these disables, may still cause power sag on the power rails and cause the currently running code to crash. (e.g. ccovell's tapedump)
The pin numbers you provided are not consistent with what it says on the
wiki.
I think it could be a little simpler with these corrections:
disabled slot:
CPU M2 (tied low for cart) yes
CPU /ROMSEL (tied high for cart) yes
CPU /IRQ (high impedence) yes
PPU /RD (tied high) this is generally /OE not needed if you disable via /CE
PPU /WR (tied high) normally /WE not needed if /CE is switched
CIRAM /CE (tied high) yes unless you never play the few 4screen mirrored games
CIRAM A10 (high impedence) yes
You may also want to tie
CPU A14 (low) agree that you can get by without since m2 is disabled
PPU A13 (high) if you switch this you won't have to switch chr /rd and /wr above
PPU /A13 (high) only needed if you wanted to play the few rare games with 4screen mirroring
For anyone curious the reasoning behind why you can't just switch power is because the chip can actually be weakly powered through the address and data lines. Typically done by the internal ESD diodes on most inputs. So really you don't fully power down the chip by just removing Vcc.
If I understand your project quentin.lamamy, it seems that is is an AWFUL lot of hardware and circuitry needed to avoid only a small inconvenience. Also why have separate slots for French and us 72 pin carts? Your using a single CIClone to disable lockout permanently. So in effect having separate slots for FR/US carts is the same as having 2 identical 72 pin slots. Unless your somehow switching from PAL to NTSC. But since you require no modification to the NES this doesn't seem possible without 2 separate NES units...
If you wanted to switch ALL 72/60 pins you could use any 5v compadible bus transceiver. Search that and it should be easy to find on any supplier site. Keep in mind you might only find fine pitch surface mount solutions.
And "tied low" means wired to ground.