Reading HP67 ROMs

[teenix]

Hi all,

Struggling to do anything boxed up in a small caravan, but I have a processor hooked onto a HP-67 CPU board monitoring the PHi 1 and 2, Sync and Is buses.

The top half of the image shows the first 3 instructions executed after switch on, the upper and lower traces are from the 67 sync and Is buses and the middle is the Is output from my processor after it decoded the Is information, fetched the ROM code and then output it to a test Is bus.

Code:


Addr  Hex  Disassembled Code
$0000 000  no operation                
$0001 3E3  if no carry go to $0F8      
$00F8 11A  0 -> c[w]

The lower half of the image is a close up of the bus signals. Mine is inverted (center trace) because it interacts with an external open source bus driver.

The next stage is to see if my processor can take over the functions of a 67 ROM by itself. The 67 CPU board I am using has a dead 1818-0232 ROM so hopefully it will spring back into life.

cheers

Tony