Reading HP67 ROMs

[teenix]

The the ROM IC Is and Data pins are both bi-directional because they read and write data. Sync, Phi1 and Phi2 are inputs.

It may just be a faulty ROM in which case you will see invalid data on the Is bus when that ROM is accessed. I used my emulator code flow printout to follow the code execution and relate it to what I saw on the scope. As mentioned, it works but is time consuming.

I will try to get some pictures of the bus activity today if I get time.

cheers

Tony

(05-05-2022 10:53 PM)Marcovecchio Wrote:  Thanks for your reply, Tony!

I'll try to analyze the signals to see if I can understand them. My main problem here is that the calculators aren't working, but I'll try!

By the way, do know which pins are inputs and outputs? I mean the Isa and data pins, in particular. Or do they change roles during operation? Well, I guess I can try turning the calculator on with and without the ACT and other chips to watch and deduce pin behavior, but any additional info is greatly appreciated!

Many thanks,

Eduardo