Hello.
I just got an old Super Sprint board and wanted to put some game in.
Pictures:
https://drive.google.com/open?id=0B0OtMD7uFlqgd2xIWmdTLWhFaWc
https://drive.google.com/open?id=0B0OtMD7uFlqgX0VzRUNRUlFpT2c
Since it's totally naked and I don't have the old componnents, I decided to put a nice game on it.
I choose Bisqwit's translation of Castlevania II. Awesome work of him, and even have an option to make it mapper 2 compatible!!
So far, so good. I put an extra little board with an 74HC161 and an 74LS32, wired it up and the game ran just fine.
Pictures:
https://drive.google.com/open?id=0B0OtM ... U1qN3dmYk0
https://drive.google.com/open?id=0B0OtM ... ERqVW5NNzQ
Now, I just wanted to use the save RAM support on it, I got a small 6116 from an old famiclone board.
I was thinking in put the SRAM on the space above the CHR RAM, but I would need to make a nasty rat's nest to plug it on the CPU BUS, so I soldered it under the PRG ROM.
Trying to make things easier, I Plugged the PRG ROM /OE to GND, so I only needed to rewire 3 pins (/CE, /WE and VCC).
I took a look at the wiki, seems that a 4 input NAND is enough to decode the PRG RAM's address. Since I could not find one, I decided to try a 74HC138 I had laying around. This is how I wired it:
And I tied SRAM's /WE to CPU R/W. For testing I left the battery out, put a 1N4148 diode on the board's VCC and the SRAM VCC like this:
So far, so good. The game detects the SRAM's presence and allows me to save.
I just save and leave the save screen, when I enter it again, the save is not there anynmore.
My main doubt is: Did my logic make sense? Should this be working? Since I got the parts from the junk pile there's a big possibility to have got some bad componnent.
Before doing this, I asked the author if a SRAM protection would be needed, he told me that not, and I needed to decode address in $6000-$7FFF range, but $0000-$7FFF is fine and only bit 15 is needed.
Does this mean I can just throw a NAND in /ROMSEL and M2 to do the job?
I have no pictures of how the board is now, but I sure can take some later and post if needed.
Edit: Corrected the naked board's picture, since the were both the same.
I just got an old Super Sprint board and wanted to put some game in.
Pictures:
https://drive.google.com/open?id=0B0OtMD7uFlqgd2xIWmdTLWhFaWc
https://drive.google.com/open?id=0B0OtMD7uFlqgX0VzRUNRUlFpT2c
Since it's totally naked and I don't have the old componnents, I decided to put a nice game on it.
I choose Bisqwit's translation of Castlevania II. Awesome work of him, and even have an option to make it mapper 2 compatible!!
So far, so good. I put an extra little board with an 74HC161 and an 74LS32, wired it up and the game ran just fine.
Pictures:
https://drive.google.com/open?id=0B0OtM ... U1qN3dmYk0
https://drive.google.com/open?id=0B0OtM ... ERqVW5NNzQ
Now, I just wanted to use the save RAM support on it, I got a small 6116 from an old famiclone board.
I was thinking in put the SRAM on the space above the CHR RAM, but I would need to make a nasty rat's nest to plug it on the CPU BUS, so I soldered it under the PRG ROM.
Trying to make things easier, I Plugged the PRG ROM /OE to GND, so I only needed to rewire 3 pins (/CE, /WE and VCC).
I took a look at the wiki, seems that a 4 input NAND is enough to decode the PRG RAM's address. Since I could not find one, I decided to try a 74HC138 I had laying around. This is how I wired it:
Code:
.-v-.
M2 -| |- VCC
CPU A13 -| |- NC
CPU A14 -| |- NC
GND -| |- NC
GND -| |- NC
/ROMSEL -| |- NC
SRAM /CE -| |- NC
GND -| |- NC
`---'
M2 -| |- VCC
CPU A13 -| |- NC
CPU A14 -| |- NC
GND -| |- NC
GND -| |- NC
/ROMSEL -| |- NC
SRAM /CE -| |- NC
GND -| |- NC
`---'
And I tied SRAM's /WE to CPU R/W. For testing I left the battery out, put a 1N4148 diode on the board's VCC and the SRAM VCC like this:
Code:
NES VCC --->|--- SRAM VCC
So far, so good. The game detects the SRAM's presence and allows me to save.
I just save and leave the save screen, when I enter it again, the save is not there anynmore.
My main doubt is: Did my logic make sense? Should this be working? Since I got the parts from the junk pile there's a big possibility to have got some bad componnent.
Before doing this, I asked the author if a SRAM protection would be needed, he told me that not, and I needed to decode address in $6000-$7FFF range, but $0000-$7FFF is fine and only bit 15 is needed.
Does this mean I can just throw a NAND in /ROMSEL and M2 to do the job?
I have no pictures of how the board is now, but I sure can take some later and post if needed.
Edit: Corrected the naked board's picture, since the were both the same.