Reading HP67 ROMs

[teenix]

My pleasure :-)

I have just finished my own ROM reader circuit which should also access the ROM's RAM data storage. It is based on a cheap PIC16F18346. It has a dual +6.25V and -12V supply. +5V is tapped from the +6.25V to power the PIC.

The PIC can control the -12V Phi1, Phi2 signal and the +6.25V SYNC signals. It also has logic level shifting to read or write the signals on the Data and Is lines. The component cost including a small mains center tapped transformer cost about $Aus25.00. PC comms is via USB using a cheap FTDI board and has re-flash capability.

I am going to try clocking the ROMs at a lower frequency so I can transfer data to/from the PC without the need for a high speed interface.

If it works, I'll publish the project on my web page.

cheers

Tony

(05-08-2022 01:30 AM)Marcovecchio Wrote:  Tony, I have no words to thank you for your kindness! Many, many thanks, for your effort and time, this is invaluable info for our community.

As soon as I have some free time, I will study the signals and try to understand them. Hopefully someday I'll be able to build some hardware to interface to these memory chips and test them.

Eduardo