ROL’s current memory map supports two 8K EEPROMS for its software. So far, I’ve only been using ROM 0 at address $e000 to $ffff and ROM 1, at $c000 to $dfff, has been stuck in the breadboard, filled with $EAs (the 6502 NOP). The chips I’m using are some AT28HC64Bs. These chips are 150ns. With… Continue reading The EEPROM

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The Jump Bug

In the last post, I mentioned a bug I was working on that would cause all 0s to appear on the data bus after a JSR instruction was executed. This bug turned out to be way more elusive and time-sinking than it should have been. When I had finished wiring up the basic system (EEPROMs,… Continue reading The Jump Bug