Reading HP67 ROMs

[teenix]

I am putting something together for myself now. I was going to get some components tomorrow to get started.

The timing diagrams supplied in the 97 service manual give some idea, and I have some info in my Classic Notes pdf, although that info is not directly related to the type of ROMs in the 67. Once I play around a bit, I will publish what I find.

Using an oscilloscope, you can analyze the waveforms on the Is and Data busses to see what is going on.

You will also need a -12V and a 6.25V rail plus Phi1 and Phi2 and sync signals. The Arduino will need to cope with the 6V signals on the busses.

The only thing I'm not sure of is how the busses are driven. I "think" they are pulled Logic HI when asserted, and require a pull down resistor, but I am not sure. The other thing I'm not sure of is whether the ROMs react to the instructions on the Is bus as well as the address info. They need to monitor the sync bus because this has an effect on addressing also, depending on what instruction executes. However, just for reading the ROM, I don't think this will matter.

Eric Smith did his "ROM Sucker" project for private use but has no details. I did try to make contact recently but had no luck.

Aside from being time consuming, it is not too hard to monitor the ROM busses and determine where a fault may lie. I have detected faulty ROMs and ARC in the past.

cheers

Tony