SNES M27C801 2in1 HiRom games - Diagram for Flip-flop 74HC74

[Kayumba]

Hi everyone,
I have .BIN file with 2 games of 4Mbit size (total 8Mbit).
I programmed M27C801 EPROM and would like to use 74HC74 Flip-flop on my PCB to switch between games with reset button.

Can somebody help me to find diagram for Flip-flop 74HC74 and M27C801 EPROM 2in1 HiRom games ?
How I have to connect 74HC74 to switch between 2 HiROM games in one M27C801 EPROM ?
Thaks for help

[lidnariq]

You can figure out how to do HiROM on your own, just like the last time you asked for LoROM reproduction instructions.

To use a 74HC74 to toggle between two halves:

1- Use half of the 74'74 to invert SNES /RESET to generate +RESET.
1a- On this half, tie CLK, D, and 74'74 /CLEAR low.
1b- Connect SNES /RESET to 74'74 /PRESET.
1c- Use 74'74 +Q as SNES +RESET. previous mention.

2- Use other half of 74'74 to alternate every time reset is pressed.
2a- Use generated SNES +RESET as above for CLK input for this half
2b- Connect /Q to D for this half
2c- Connect +Q to ROM address line
2d- tie /CLEAR and /PRESET high


This thread belongs in forum "Reproduction".

[Kayumba]

OMG!
Thank you for help and sorry but i'am lost...
I see nothing like /Q or D and +Q ...

Where is /CLEAR low or just/CLEAR
/PRESET high or +PRESET

I tried to understand with my drawing schema, but I think i'am lost...



2b- Connect /Q to D for this half
Where is /Q ?

2c- Connect +Q to ROM address line
Where is ROM adress line for 8Mbit game in M27C801?
Where is ROM adress line for 4Mbit game in M27C801?

Do you have schematic draw please?

[lidnariq]

I see nothing like /Q or D and +Q ...

D is "Data In".
Q is "Data Out"
/Q is "Data out" with the line over the top.
The line over the top means that the output is logically inverted (that is, a low voltage means "true")

[Kayumba]

OK,
Thats mean +Q is it "Data Out 1" ?

And where is ROM adress line for 4Mbit game in M27C801?

Can you tell me, please if on my draw its all right ?

[Kayumba]

Why this diagram works only with LoRom?

[lidnariq]

OK,
Thats mean +Q is it "Data Out 1" ?

Yes.

And where is ROM adress line for 4Mbit game in M27C801?

Depends on how you put the data into the ROM.

Can you tell me, please if on my draw its all right ?

Code: Select all

 gnd -- /1clr | 01   14 | vcc -- vcc
    gnd -- D1 | 02   13 | /2clear -- brown
  gnd -- Clk1 | 03   12 | D2 -- cyan
blue -- /1pre | 04   11 | Clk2 -- purple
 purple -- Q1 | 05   10 | /2pre -- brown
    nc -- /Q1 | 06   09 | Q2 -- grey
   gnd -- gnd | 07   08 | /Q2 -- cyan

All correct, except tie /2clear and /2pre to vcc also.

Why this diagram works only with LoRom?

It is important to make sure that the 74'74's output changes before the SNES starts fetching data from ROM. Otherwise it'll fetch data from both halves of the multicart, and most likely crash. That's why I added the inverter above.

[Kayumba]

Great!
Thank you for help.

Look the final diagram with your corrections:



I will try to test it this week-end.

I have some questions...

And where is ROM adress line for 4Mbit game in M27C801?
Depends on how you put the data into the ROM.

I use HEX editor "free-hex-editor-neo"

I open game in HEX editor "free-hex-editor-neo" to make copy and past the second game at the end of first, then save it.
Or I use second method with command line, like :

Code: Select all

copy /B "game1.sfc" + "game2.sfc" two-hirom-games.sfc

Will this two different methods change the address line of ROM ?
How can I see it ans test it?
To what number of pin at 27C801 can I connect 74'74 pin 09 | Q2 (Data Tout 2) ?

Will this diagram also work with LoROM games ?

Thanks again.

[lidnariq]

paste the second game at the end of first, then save it.
Or I use second method with command line, like :

Code: Select all

copy /B "game1.sfc" + "game2.sfc" two-hirom-games.sfc

In this case, where you are combining two 512KiB files to make one 1 MiB file, and placing the result in a 1MB UVEPROM that's 1048576 x 8 bit, this means that the 74'74 should be connected to A19.

Will this diagram also work with LoROM games ?

Well, what differs between LoROM and HiROM?

[Kayumba]

paste the second game at the end of first, then save it.
Or I use second method with command line, like :

Code: Select all

copy /B "game1.sfc" + "game2.sfc" two-hirom-games.sfc

In this case, where you are combining two 512KiB files to make one 1 MiB file, and placing the result in a 1MB UVEPROM that's 1048576 x 8 bit, this means that the 74'74 should be connected to A19.

Will this diagram also work with LoROM games ?

Well, what differs between LoROM and HiROM?

Well, if I understand right...
In 27C801 pin1 is originally A19 , but to use with PCB, A19 should be pin30.
So that why we need to make SWAP BIN method for ROM files.
After made SWAP BIN to ROM file (with soft utility), originally pin1 A19 in EPROM became A17.
And A19 is moved to pin30 (swapped to pin30).

So, normally, if I get it right...
For HiROM games pin9 (data output 2) of 74'74 should be connected to pin30 of M27C801 (which is became A19 after have made swap bin to file) .
And this A19 (pin30)=> are connected to cartridge connector 44.

For 27C801 LoROM games pin9 (data output 2) of 74'74 should be connected to pin30 of M27C801 (which is became A19 after have made swap bin to file) .
And this A19 (pin30)=> are connected to cartridge connector 45.

Is that right?
Or you mean connect to originally A19 of 27C801 (before swapped bin) in pin1?

[lidnariq]

Why are you swapping the pins around?

[Kayumba]

Why are you swapping the pins around?

Why?
Thats why :

[lidnariq]

That doesn't explain anything...

[Kayumba]

That doesn't explain anything...

I dont understand your question also...
I think you know better than me for what for we nee to do SWAP BIN method.

Explanation of SwapBin :
pin 1 on the 27C801 is A19, but on the SNES PCB, this pin is A17.
So, instead of having to rewire A17 and A19 to different places, we can use software to digitally swap these two address pins by modifying the hex code. That way, we effectively change the pinout of the 27C801.

SNES ROM Utility switches A19 with A17 and A16 with A18.

[lidnariq]

Have you already made a reproduction without using the 74'74? If so, what did you do there?