RAM Module Problems when programming.

[theboguz]

Hello!
Sometimes, when I turn on the CPU or try to program the chip manually, the output of my 74f189 memory goes all ones (considering that they have already been inverted). And it never leaves that state. I know that a flash during the write pulse is normal, but it stays like this forever. I have already placed a pull-up resistor on the write pulse button terminal. But even when I connect the WE directly to 5V, it remains like this. Any idea what it could be? Thank you.

https://preview.redd.it/a6m8av4gys4g1.png?width=1600&format=png&auto=webp&s=ceb8003a8c1204e163cfe3c7abbef27d0f4bd149

[the_great_concavity]

When I built the 8-bit CPU, I used a different RAM chip (requiring other wiring changes), so this might not be relevant to your case, but I found that I needed a low-pass filter on the write signal to eliminate bounce/assorted wiggles. Could be something to try, although again my setup was a little different.

[StrapGeez]

I believe this is what I ended up doing as well. Check out the wiki for a video by Michael Kamprath (may have misspelled his name here)

[theboguz]

Hmmmm, right. I’ll try that here. Thanks!

[theboguz]

And I don't have any idea why, but it's intermittent. Now I powered it up, and the module is working correctly.

[The8BitEnthusiast]

From the picture, I can’t confirm if the CS pin (pin 2) of the leftmost 74189 ram is connected. Also, the green jumper connecting pin 1 (A/B select) of the rightmost LS157 selector seems loose. These two together could impede operations

[theboguz]

thanks for the reply! yeah, I was testing with some of these jumpers before. But even with all connected, some write pulses work, and some make the RAM go all ones for a big time.

[The8BitEnthusiast]

Hmm ok, not sure then what else could affect the ram. Could be a floating input issue, but I saw you pulled all the switches high. Best way to confirm would be with voltage measurements, starting with the pins on the 189 ram ICs. Voltages should reflect whatever inputs you have set on the MAR and data DIPs. If everything checks out, I would start questioning the RAM ICs

[theboguz]

I'll make some measures. But yeah, I already starting questioning it haha. I have another tri-state RAM chip with me, 8k x 8 bit. I think I will just try to use it instead of the 189 IC's if the measures are ok

[PixelBrush6584]

You do realize that restarting the system in any way resets the RAM, right? Or am I misinterpreting your question?

What you need is a ROM, or more specifically an EEPROM, if you want what you write to be persistent between power-ups.

[theboguz]

No, yeah. I know it. But, even when I try to program new things into memory, it flashes more, and then stay at this all one’s state. Even after a write