Hey Artemio. I know it's a long shot to ask here, but I am running the 240P Test Suite on a Genesis ROM cart. I am doing the Sega CD hardware tests, and I get this error for the Program RAM. I am getting this on 2 different Sega CD's. Because of this, I can never get the animation of the SEGA logo to show up on the screen.
"The register did R/W OK, but the bank switch was either not done or RAM is bad. Try memory Viewer at address above (0x000000420000) and use C"
What does this message mean, and what can I do about it? I checked that memory area, but I don't know what to do once I look in there and don't know what it's supposed to say.
(Ignore this) I have checked both RAM banks' (65256BLFP-10T) traces which route to SEGA's 315-5476A IC. I have continuity between both RAM banks on all Pins except for Pin 20 which is supposed to be separate, and continuity is there between the RAM banks and the IC 315-5479A. (EDIT: This is the sound source RAM and has nothing to do with what I was looking for.) (/Ignore this)
I also tried a board swap with a known working SEGA CD, and the problem follows the board.
I also tried replacing the RAM with LH52B256N-70LL. The same thing happened, so I put the old RAM back on.
Is there somewhere else I should check?
Thank you in advance for any advice you can spare.
Hello, I was away when you posted this and showed to L Oliveira. As you stated that was PCM RAM, and the other is the backup RAM.
You'll need to check all control lines as well as address and data lines. Check out this diagram: https://www.retrosix.wiki/hardware-overview-sega-mega-cd
No worries. Right before you replied, I just found three severes traces from a leaky capacitor. And those 3 traces go directly to the the Program RAM.
It's a lot easier to find this stuff when you're checking the correct ICs. Who knew?
Thank you for the reply, and I appreciate that 240P test suite. It was a life saver.
Program RAM is 4 banks of 131072. So it should be the dual chips at:
- IC108: SRAM: LH5P832N-10
- IC109: SRAM: LH5P832N-10
Keep in mind anything in the path form the CPU to the program RAM could be damaged: traces, logic, etc.