Snes MultiCart Question (Switch)

[Limewater]

I tried it with m27c160 and another repro board



On this i am using a19 biggest address available when it is tied to vcc the first game works and when it is tied to gnd i m getting black screen.

Bottom Line Up Front: I think you probably have your switch hooked up to the wrong address pin.

Let me see if I understand the situation.

First, you followed a tutorial to create a two-game image for the M27C801 (1Mbx8) EPROM on a more standard SNES PCB. This packs one game starting at address 0x0_0000 and another starting at 0x8_0000. It switched between the two games just fine. Success.

Note: I may be misunderstanding something here, since the video appears to be in Portguese, and I don't speak it. It kind of looks like he hooked the switch up to pin 30, which is A17, NOT the highest-order bit. That would make it look like the games are smaller, with game 0 starting at 0x0_0000 and game 1 starting at 0x2_0000. Is Top Gear just a 2MBit game?

Then, you moved to the mousebitelabs PCB, which takes 16-bit-word EPROMS.
For the M27C322 (2Mbx16). I don't have a schematic of the mousebitelabs board, so I am kind of guessing here. He mentioned using a mux to read each of the two bytes in each 16-bit word. That makes me thing that the Address0 signal from the SNES is actually running to the mux, and the rest of the address lines are down-shifted accordingly.

Regardless, if you are using the same two-game image you used in the M27C801, you should not be using the highest-order address bit to switch between the two. That will just set the SNES looking at unprogrammed memory. Rather, you need to be toggling the appropriate address bit.

This is still based upon some guesses on my part, but:

IF you successfully build a two-game image that works on the M27C801 then:

Note which address pin you have your switch hooked up to. Check the data sheet to figure out which address bit it is.
Subtract 1 from that address bit. So, if it's A19, subtract 1 to get A18.
Figure out which pin on the M27C322 is A18.
Hook your switch to that one.

The process should be the same with the m27c160.

EDIT TO ADD:
Are you sure that the first game is loading properly when you have that high address pin pulled hooked to Vcc and it's failing to load when it's grounded? That seems backwards to me, but I didn't check that part of the datasheets. Are the address pins inverted?

[Ziggy]

What are the size of your games?

If you're switching the highest address line, that'll make the cart see two halves of the EPROM. So on your 27C322, it'll see two 16Mb halves. If you're programming your EPROM by combining the two game ROM files first, you have to make sure they are both 16Mb before programing. If they are smaller, you have to pad them out first. Otherwise your first game will be at the start as expected, and work when the switch is in one position, but then your second game wont be in the correct location.

[Limewater]

Assuming Ziggy and I are right and you're going to be changing which address pin you have hooked to your switch, you might want to get something like this:

https://www.testequity.com/product/3429 ... GSEALw_wcB

You don't have to get this exact one. It's very expensive. It's just the first one that popped up when I searched for it.

You can use it to clip onto a lead on your EPROM and clip the other end to your wire or switch. This way, you can make sure you have selected the correct pin before soldering to it.

Don't try it with alligator clips, though. You'll just short to neighboring pins.

[hidden0]

I tried it with m27c160 and another repro board



On this i am using a19 biggest address available when it is tied to vcc the first game works and when it is tied to gnd i m getting black screen.

Bottom Line Up Front: I think you probably have your switch hooked up to the wrong address pin.

Let me see if I understand the situation.

First, you followed a tutorial to create a two-game image for the M27C801 (1Mbx8) EPROM on a more standard SNES PCB. This packs one game starting at address 0x0_0000 and another starting at 0x8_0000. It switched between the two games just fine. Success.

Note: I may be misunderstanding something here, since the video appears to be in Portguese, and I don't speak it. It kind of looks like he hooked the switch up to pin 30, which is A17, NOT the highest-order bit. That would make it look like the games are smaller, with game 0 starting at 0x0_0000 and game 1 starting at 0x2_0000. Is Top Gear just a 2MBit game?

Then, you moved to the mousebitelabs PCB, which takes 16-bit-word EPROMS.
For the M27C322 (2Mbx16). I don't have a schematic of the mousebitelabs board, so I am kind of guessing here. He mentioned using a mux to read each of the two bytes in each 16-bit word. That makes me thing that the Address0 signal from the SNES is actually running to the mux, and the rest of the address lines are down-shifted accordingly.

Regardless, if you are using the same two-game image you used in the M27C801, you should not be using the highest-order address bit to switch between the two. That will just set the SNES looking at unprogrammed memory. Rather, you need to be toggling the appropriate address bit.

This is still based upon some guesses on my part, but:

IF you successfully build a two-game image that works on the M27C801 then:

Note which address pin you have your switch hooked up to. Check the data sheet to figure out which address bit it is.
Subtract 1 from that address bit. So, if it's A19, subtract 1 to get A18.
Figure out which pin on the M27C322 is A18.
Hook your switch to that one.

The process should be the same with the m27c160.

EDIT TO ADD:
Are you sure that the first game is loading properly when you have that high address pin pulled hooked to Vcc and it's failing to load when it's grounded? That seems backwards to me, but I didn't check that part of the datasheets. Are the address pins inverted?

So Regarding All that First of all i used a normal standard Snes board with m27c160 Adapter Burned two games like they are suppose to be 1+1 MB games.

Then I used A18 Like you suggested becuz indeed it was going from A19 from Standard Maskrom/M27c801 to A18 on m27c160 but it didn't work so i tried the Biggest A19 with a Switch and it worked fine both games loaded with switching.

Then i Tried another repro board The Green one without the Multiplexer 74xx257 one. And it also worked fine Then i used it with Advance Mousebitlabs board with 27c322 support and the one have 74hc257 Chips and Same Thing One game worked And when it switch it Console Doesn't Turn On ( Some sort of short i believe ).

So I think there are some more things needs switching in multiplexer chips or anything i don't really know how that works tbh.

2ndly :

I want to make a Multicart with Sram and DSP chip.
What i understand i need to Lift Pin A19 + Sram Pin2 and attach it with the switch with same VCC and GND and it should work ? Am i right or is there anything else i need to do ?

And What about The Multicart with m27c322 + Multiplexer chips how they will work ?

[hidden0]

What are the size of your games?

If you're switching the highest address line, that'll make the cart see two halves of the EPROM. So on your 27C322, it'll see two 16Mb halves. If you're programming your EPROM by combining the two game ROM files first, you have to make sure they are both 16Mb before programing. If they are smaller, you have to pad them out first. Otherwise your first game will be at the start as expected, and work when the switch is in one position, but then your second game wont be in the correct location.

Yes i first i expanded roms separately 2+2MB or 1+1MB and then combined it , That part i understand correctly and it worked the problem is something else with m27c322 and the multiplexer i think.

[hidden0]

Assuming Ziggy and I are right and you're going to be changing which address pin you have hooked to your switch, you might want to get something like this:

https://www.testequity.com/product/3429 ... GSEALw_wcB

You don't have to get this exact one. It's very expensive. It's just the first one that popped up when I searched for it.

You can use it to clip onto a lead on your EPROM and clip the other end to your wire or switch. This way, you can make sure you have selected the correct pin before soldering to it.

Don't try it with alligator clips, though. You'll just short to neighboring pins.

I am very good at soldering so it's not really an issue .

[Ziggy]

When you first posted, I was thinking it could be a possible issue because of the 257's, but I didn't say it because I don't know WHY it would be a problem.

[hidden0]

When you first posted, I was thinking it could be a possible issue because of the 257's, but I didn't say it because I don't know WHY it would be a problem.

So Wiring Multiplexer 257 Is the issue here there must be a way around , or method i believe.
I'll keep searching and updating please let me know if you find anything about it .

+ About the Mario Kart Multicart , Problem i am facing is Assuming we need Double the SRAM as used by the tutorial and Mario Kart has 24 Pin SRAM and 64K ram is 28 pin so manual wiring might be needed ?

+ i can't really find any English guides or info But i m thinking lifting A19 + Sram Pin2 I think A12 combines both of them And Connect to a switch with VCC and GND would be it ?

Figured Out the ISSUE , It was a stupid mistake on Advance mousebitelabs pcb that the m27c160 pulled pin was touching the Console cartridge slot and causing the short.
That 2MB IC worked fine as well on that board now moving upto m27c322 will up date you guys.

[hidden0]

Issue solved regarding m27c322 check the main post.