6502 cannot read from ROM after connecting to 6522

#1 · October 17, 2025, 3:31 pm

I'm trying to mimic what Ben Eater posted on YouTube, after wiring up components, it seems working propaly until I connect the clock (PHI2) on 6522, then all of sudden the processor no longer be able to read from ROM anymore, if I disconnect the connection to 6522's clock, then the reading is back to normal.

I don't know what I did wrong, but everything seems logical.

Uploaded files:

6502.sim1

#2 · October 17, 2025, 3:45 pm

I found my own silly mistake, I miss wire the output of Address bit 15 to the NAND gate. I should have wired it from the output of first NAND result, not directly from bit 15.

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