Thread: hp-41cx / NoV-64d / Hepax XF multi-function

[MeindertKuipers]

I see nearly the same behavior after clearing the HEPAX memory.

However, my HP41CX does power off correctly, and when powering on shows FAT FULL. A subsequent power cycle turns everything back to normal. I had only HEPAX-1D loaded, not the other HEPAX support modules.

I have now hooked up my newly builtHP41 bus analyzer and will share the results.

In addition I see that the HEPRAM page in page B is messed up, the BCAT of Page 9 shows "@@@@@@@@@@@". Details of this page:
9000 - 00C
9001 - 02F
9002 - 000
9003 - 000

The HEPAX chain looks quite OK, with all pages initialized (200 in xFF3). A bit funny is that Page 9 is the first page in the HEPRAM chain, then A, B and finally 8. HEPROOM gives the correct result.

I have put the traces (hexcodes only, no disassembly) on my GitHub page here: https://github.com/mjakuipers/NoVRAM-HEPAX-traces

I did a quick scan, and in the trace where XF 000 is entered in the program, I see a bankswitch instruction to Bank 3 (traceline 7020 in the file '3-enter XF in PRGM mode.txt'), but never a bankswitch back to bank 0. This would perfectly explain the behavior that a BST cannot find the function again, as the main HEPAX bank with the FAT is gone. Power cycle will more or less fix this but with the wrong bank active strange things may happen.

Why is this happening? May be due to something in PRGM mode since the HEPAX XF function does ask for a 3-digit prompt like it is executing, but it never executes, the XF code is entered in program memory. But a quick test on my HP41CL works as expected (and it would be difficult to make a trace as this will probably not show on the HP41 bus).
Alternatively the NoVRAM firmware may have the enabled bank a bit more sticky than intended and does not automatically switch back to bank 0 in this situation.

My tests are done with my NoVRAM64d, loaded with HEPAX-1D and 4 HEPRAM pages in an HP41CX, nothing else.