Bregalad, this is for you

Banshaku · Post by **Banshaku** » Sat Nov 22, 2008 6:26 am

People are not aware about it since we were talking in private about this subject but you really wanted to see Best Play Baseball special, how it look like since it's a special SXROM board. I said if I find it, I will try to open it.

I kept my promise. I had a hard time but tonight I was able to make my custom screwdriver and it worked. I hope the information will contribute everyone.

Here's the pictures, not prepared yet properly for the bootgod database:

The opened card with the box and my custom screwdriver

The front of pcb

- The top chip is written sn74HCUO4N
- It's a MMC1B2
- HVC-SXROM-01

The back of pcb

Cover of cart

The front of the box

I hope you're now happy to see it. I will try to open a few other ones if I can find the time to do it.

Bregalad · Post by **Bregalad** » Sat Nov 22, 2008 6:49 am

Oh this is awseome.
It would be great to definitely know where A13 and A14 (pin 26 and 1 respectively) of the 32kb SRAM chip (maked Yundai 62256) connects.

Normally they should connect to MMC1 pins 9 and 10 (CHR A15 and A16) respectively, but I never had any confirmation on this. It's impossible to see where they connect with only the pictures, but if you have an ohm-meter and could veryfiy that it would be great.

Also, pin 6 of MMC1 (CE) should connect to pin 1 of the 'HCU04 and pin 2 of the 'HCU04 to pin 20 (/CE) of the SRAM. Pin 22 (/OE) should be connected to GND. Then all other pins of the HCU04 would be connected to nothing signigicant, as this chip probably only serves to invert the CE signal.

If you could possibly veryfy all of that, it would be awesome, and confirm all our hypotesis about the SXROM board.

Banshaku · Post by **Banshaku** » Sat Nov 22, 2008 7:07 am

Good to see you're happy about this.

You're in luck: I do have a ohm meter since I bought one back recently because I need it to built my dev carts soon. Good chance I will be asking many questions about it since my attempt may (actually will) fail on my first try -_-;;

Good thing I didn't close the cart before reading that post. I will check it right away and see what I can do. I'm a little bit exhausted thought, so I hope I won't do any mistake

Banshaku · Post by **Banshaku** » Sat Nov 22, 2008 8:21 am

This is the results so far:

[SRAM]
- Pin 1 of SRAM do connect to pin 10 of MMC1
- Pin 26 of SRAM do not connect to pin 9 of MMC1. It seems to connect to the same pins as 30th of PRG and one pin on connector
- Pin 17 of SRAM connects to pin 9 of MMC1
- Pin 20 of SRAM is useless info. I made mistake with 22
- pin 22 of SRAM connects to the same pings as 26 of PRG, which connect to back of the 3rd connector's pin from the left. I don't know if this mean /CE since I don't have any electronic background. Please confirm.

[HCU04]
- Pin 1 of HCU04 do connect to pin 6 of MMC1
- Pin 2 of HCU04 do not connect to pin 20 of SRAM. It connects to the 23rd one.
- All other pins of HCU04 do not connect to anything particular

This is what I have for now. I'm no expert and I can do more test if I'm guided in the right direction.

Bregalad · Post by **Bregalad** » Sat Nov 22, 2008 11:21 am

Oh, pintouts for the chips are numbered counter clockwise. When you reach the second half of a DIP chip, you continue to cout pins in the other direction, you don't get back to the bottom to count up on the other side. Sorry I haven't mentionned that, I was under the impression you knowned that.

It seems that SRAM pin 28 (that you labelled 17) actually connects to pin 9 of MMC1, which means the full 32kb of SRAM is adressable as it was previously expected. This is good news.

Banshaku · Post by **Banshaku** » Sun Nov 23, 2008 7:03 am

Doh! ... You are correct, I didn't know about the pin order. I was right for the first row but completely wrong for the second one. Sorry about that. Like I mentioned, I was exhausted yesterday so I didn't saw that detail at all.

I just retested everything and here's the updated results:

[SRAM]
- Pin 1 of SRAM do connect to pin 10 of MMC1
- Pin 26 of SRAM do connect to pin 9 of MMC1
- pin 22 of SRAM connects to what seems to be GND

[HCU04]
- Pin 1 of HCU04 do connect to pin 6 of MMC1
- Pin 2 of HCU04 do connect to pin 20 of SRAM
- All other pins of HCU04 do not connect to anything particular

So everything seems to be like you expected. I will leave the cart open for a few days just in case if you still have other questions about it.

This is a good thing that I did that. Without this, I would have made quite a mess with the pin order while doing my dev cart -_-;;

Off topic, did people in the past asked about the meaning of VCC, CE etc? I would love to know more about that. I will do a quick search in the forum, maybe it's there.

Bregalad · Post by **Bregalad** » Sun Nov 23, 2008 7:50 am

Oh thank you very much. It's great it's exactly like expected !
And is opening and closing carts that bothersome ? Sice I have a tool I can open and close cart as much as I like, this isn't really an issue.
I do not have any more questions. Oh while we're at it, copyright which year Nintendo ? I guess it doesn't matter but for some reason I can't read the number, but I don't really care.

atari2600a · Post by **atari2600a** » Sun Nov 23, 2008 12:08 pm

ASCII?

Banshaku · Post by **Banshaku** » Sun Nov 23, 2008 5:31 pm

Bregalad wrote:And is opening and closing carts that bothersome ? Sice I have a tool I can open and close cart as much as I like, this isn't really an issue.

Since my tool is homemade, it doesn't grip the screw very well and tend to damage the inside of the holes and the screws. I just don't want to damage the case too much since I'm still a collector after all

Bregalad wrote: I do not have any more questions. Oh while we're at it, copyright which year Nintendo ? I guess it doesn't matter but for some reason I can't read the number, but I don't really care.

It's was hard to read since it's under a component. It's written 1991.

atari2600a wrote:ASCII?

Yes, the game was made by ASCII but the board was by nintendo if this is what you meant.