Uses Sean Riddle's dumper circuit, but with a RP Pico instead of the PIC. I ported Sean's code over to the Pico but couldn't get reliable reads, so I rewrote it to use a generic system of injecting instructions and used a more elaborate scheme to get the data out of the device. This is very much a hacked together tool specifically built to dump a ROM. It's not a finished product.
The TEST pin handling is the same as Sean's code, but I have code that can inject a (preset, in arrays) sequence of code into the device. This allowed me to debug my instruction extraction and come up with a method of reading ROM bytes reliably. As I still had issues with a value every few hundred bytes I now read each byte in the ROM many times and only if that block read gives the same value is it used as the ROM byte value. If the values aren't the same then the block of reads is re-done until it is. This means it takes a while to read the ROM but the values are, I think, correct. I checked operation with the Boris chess computer ROM and I got a dump that matched Sean's ecxept for the last few bytes which are, I think, unused values.
I then dumped the ROM from a device out of an HP82143 printer. The Boris and HP dumps are in this repository.
The PCB is powered by the Pico USB, whih also has a menu system to drive the code and get dumps.
At the moment the code always dumps 4K
This version of the PCB does not work unless you add level shifters between the Pico and the 4066 control lines. I added a couple of FETs onto my PCB manually. If you don't do this then the PCB will not work.
Here's the V1.0 PCB I used:
You can see a dc-dc converter module on the right, and the level shifters I wired in going from the 4066 to the Pico on the left. The 40 pin IC is the M3780. the two LM317T circuits are on the right with their adjustment potentiometers.
There's a menu system on the USB. Press 'h' to see the command list. To dump a ROM use 'u' then 'S' to dump the ROM. It takes a while as each byte is read, when it's done the full dumpo is displayed. There's some problem that means that you need to select 'u' before using 'S'. As this is a one or two use dumper, I'm not bothered by these wrinkles.
Sean Riddle's site: https://seanriddle.com/ Forum thread: https://www.hpmuseum.org/forum/thread-20043.html