Which pin of the 72 (or 60) can be used to disabled a slot

[quentin.lamamy]

Hi it's me again for my NES arcade cabinet project.

On my arcade cab there is 2 slot, one for the US and PAL cartridge and one for the famicom cartridge.

I am looking for a way to disable a slot, i think that disabling the +5v of a slot make it inactive but i'm not sure. Someone have an idea ?

[ninn]

Hi it's me again for my NES arcade cabinet project.

On my arcade cab there is 2 slot, one for the US and PAL cartridge and one for the famicom cartridge.

I am looking for a way to disable a slot, i think that disabling the +5v of a slot make it inactive but i'm not sure. Someone have an idea ?

So, you are asking how to disable one, after you (successfully) added one?

The TriStar/Super8 for the SNES got 2 Slots for NES and famicom too. But it will not work when both carts are inserted.

Shouldn't that be the easiest possible way to do it?

Kind regards,
ninn

[MottZilla]

I think it depends on the cartridges used and how they enable their devices. Carts that are more simple like NROM or UNROM might just have a couple enable or select signals. I think just a PRG /CE and CHR /CE (and perhaps and address line too) to determine if they should enable their chips. But more advanced mappers may ignore these signals possibly and decode when and what to enable themselves.

Looking at the cart pinout though it looks like pin #44 PRG /CE is definitely used as A15 is not otherwise there it seems. But if a cartridge maps $6000-$7FFF then you have a problem if both inserted cartridges do as you need to switch those signals off on the unused slot.

I'm sure someone else can give you more detail. But you certainly could make a multi slot device. Afterall Nintendo did that themselves.

[quentin.lamamy]

I'm sure someone else can give you more detail. But you certainly could make a multi slot device. Afterall Nintendo did that themselves.

I know that's why i try to do it ^^.

You think that disable the input of +5V in the cartridge isn't enough to disable the load of the cartridge ?

[Memblers]

You think that disable the input of +5V in the cartridge isn't enough to disable the load of the cartridge ?

Definitely not, the cartridge would draw power through the data and address lines. You would have to do it like a Playchoice-10 game board does, but a bit more because you would need to handle any given mapper.

[mikejmoffitt]

Cutting 5V will not be enough - I am not qualified to explain exactly why, but my understanding is that the inactive chips that are still connected may still fight with the other ones that are connected to the same lines, possibly pulling high signals lower than they should be, and drawing extra current.

[quentin.lamamy]

No way with just a switch on some pin ?

[ninn]

How about a Switch for 72 pins? 8)

[quentin.lamamy]

How about a Switch for 72 pins? 8)

And where do you find a switch able to work on 72 connector ?

[MottZilla]

Maybe an electronic type of switch. I guess you could get a ton of one of the 74 series chips and wire them up to a switch. =)

Again the pins you are looking for to switch simple carts are PRG /CE and CHR /RD, those are #44 and #17. CHR might be a bit more complicated though. If you make a switch on those two pins, simple mapper games would probably work with one in each slot. However for more advanced mappers you will need to switch more pins.

For PRG /CE and CHR /RD you just need to disconnect any non-active slots. That way the cartridge shouldn't attempt to respond to any reads. For mappers like MMC3 that generate IRQs, you should also disconnect the /IRQ line, pin #15.

For cartridges that contain mappers that support memory at $6000-$7FFF such as MMC1, MMC3, and more, you should also put A14 (pin #41) on a switch with two positions. Connected normally, and Grounded. The reasoning behind this is so if the mapper in a nonactive cart decodes A13&A14 as part of enabling memory at $6000 it will never see the condition.

I'm not an electrical engineer but I think that those 4 pins are what you need to wire with a switch. Disconnect or connect pins #15, #17, #44. And Pin #41 should goto ground or connect.

More might be needed for more complicated CHR bus configurations. Just curious, what are you trying to do? Modify a NES with a built in game?

[quentin.lamamy]

What i want to do an arcade cabinet from a NES. with a minimum of 3 slot :
- The first one is the boot cartridge which display a message like "please insert cartridge"
- The second a PAL / US cartridge slot
- The Third a Famicom Slot

So if i disconnect 15,17,44 and 41to ground i can disable a slot.

Now i need a system which disabled slot when a cartridge is slotted in another one ^^ (in a next topic)

Someone can valid the pin i need to disconnect or ground ?

[lidnariq]

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.

[WhoaMan]

could always use some 74244 line drivers and 74245 bus transceivers to enable and disable one slot or the other.

[quentin.lamamy]

So if i those 10 pin are grounded the slot will be disabled.
Someone can confirm ?

Any idea on the electronic component i can use to do this ?


lidnariq what the mean of what you add between "(tied low)" for example.
Can you rephrase more simply what can happened with hot plug ?

[quentin.lamamy]

could always use some 74244 line drivers and 74245 bus transceivers to enable and disable one slot or the other.

May you explain me what it is and how it work ?