HP67 running

[teenix]

Hi all,

I managed to get the HP-67 emulator and compiler working. The CRC interacts with the PC ok and will read/write the data using the hard disk instead a card.

I stumbled around for awhile and couldn't get it all to work, but found the instruction [data register -> c 0] was the culprit. I expected it to behave like the other [c 1] to [c 15] codes but not so.

I thought it was a problem in the code listing as I have found errors in the published listings for other models. For example, the HP-55 could not access the RAM banks properly and the HP-65 code went into a huge delay loop when the R/S key was pressed. After many late nights, I found and fixed those problems, but the 67 code seems ok.

In the 67, there is a code loop activated from the [f] [P<->S] key sequence that has the [data register -> c 0] instruction used in quick succession while swapping the RAM banks. It was here that I concluded the [c 0] instruction is unique in that it doesn't appear to set the lower 4 bits of the RAM address latches like the others do.

Instead, it uses the complete 6 bit address that happens to be in the address latches at the time. So if those latches contain 101111 (Bank 2) (Addr 15), [data register -> c 0] loads C from that RAM address, not (Bank 2) (Address 0) as you logically might expect.

To access RAM 0 in any bank using this instruction means the lower 4 bits in the latches must have been set to [0000] previously.

Sorry if this has been hashed out before, but I haven't seen a reference to it, and of course, apologies if I am wrong.


Adding the 67 to the hardware calculator is going to take some time because I need a different model PIC to emulate it due to the extra ROM/RAM needed. The one I chose is cheap and pin compatible but has different internal architecture and I will have to rewrite the original assembler before adding the 67 code. My old PIC programmer that I created 10 years ago sadly will need a code tweak as well.

If anyone is interested it will be available to download at teenix.org when complete.

cheers

Tony