Panasonic HHC ROM 'capules'

[Jeff_Birt]

I guess the way A12 is configured it can't pull the A12 pin on the EPROM up unless the EPROM has VCC applied.

I was also just looking at the schematics again and noticed that the 'All Off' switch does not actually disconnect power to everything. the VCC regulator is always powered. The instructions in the manual say to turn off the 'All Off' switch, plug the capsule in, then turn switch back on. The switch only disables the CPU power. Maybe the polling for ROMs takes place before the switch is turned on?

I seem to recall seeing a low-level signal on the capsule socket VCC when the 'All Off' switch was off. I dismissed it as noise as it was 'All Off'. Perhaps that is the polling process to discover ROMs? If so, I will need to wait until my capsules from eBay arrive to do further testing.