HP-97S trouble: shown 0. 00 instead of 0.00

[teenix]

That's the ROM0 chip - 1818-0267, address range $0000 - $03FF. This 18 pin IC also helps drive the LEDs.

What happens if you press the SIN or Yx buttons. Does it take a second or so before the display lights up again?

If so, maybe it is just the display formatting that is at fault. No great help, but may narrow things a bit.


With the emulator, you can also fail any ROM instruction you like.

It has an in-built assembler, so you can replace any instruction with [no operation] and the code will automatically re-compile when emulation starts.

There is also a "Restore" button that will restore the original code.

One problem with finding a bad RAM or ROM location, is that the created fault might mimic the real fault but might not be the same. The best way would be to analyze the code flow and see where it is going astray. I have done this in the past to find faults, however this is difficult without proper gear.

cheers

Tony