Hp-41 execution redirection



#9

I am trying to understand how the hp-41c transfers execution control if it sees a diagnostic module installed at page 4.

Is the Instruction Addressing hardware redirected within the cpu? Or is it just a jump to page 4 and all the instructions within that rom are hardcoded to page4 and above(an absolute code segment)?

I'd appreciate it if any gurus out there still can answer this one since I dont have a copy of the service module. I understand it was for hp internal use only......

Regards


#10

At the addresses #0180 and #01AD in the HP-41 ROM there is a GSUBNC #4000 instruction. If the diagnostic module exists then execution is transferred to the address #4000. If it doesn't exists then a simple return occurs (this is a nice feature of the Nut CPU).


#11

Forgot to say: the diagnostic module is tested every time when waking up from light or deep sleep.

#12

To be more precise, the gosub is even not executed if the target address is empty (0).
On Saturn processor (HP71B..HP49G), the 0 opcode (RTNXM: return and set external module missing) provides the same kind of function.

J-F

[Hello HarstProg!]


#13

Thanks for the correction, J-F :-)

How do you do? Are you still working on Emu42?

#14

There once was a paper from PPC about MCode, in addition a listing of the service module SM-1:C. With a ZENROM and an MLDL or adequate you may type in the 4k. Or much easier with one of the 41-emulators (from W. Fulrow, J-F Garnier, HrastProgrammer or mine if you have access to VM/ESA). Then you may use your favoured editor and make a BIN from that listing. ;-)

Hello J-F and Hrast!
After several month out of 41-business I'm about to update my site at compuserve. Could you pls sent me your valid URL for the latest revision of your emulators? TIA.

Ciao.....Mike


#15

Hi Mike ... nice to see you ...

My homepage is <http://hrastprogrammer.tripod.com>. It was updated before a month or so with the latest info about HP-41X Extended MicroCode Emulator for HP-48GX and HP-49G.


#16

Hello!

Sorry to appear only infrequent on this list. I was monopolized by my HP200LX. I just try to 'finish' my Coconut emulator "NutEm". Still looking for a way to migrate FORTRAN to an other platform.

Ciao.....Mike


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