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HP 41 Diagnostic & Service ROM
01-08-2018, 05:47 PM
Post: #1
HP 41 Diagnostic & Service ROM
So I finally completed my New Years resolution to examine 5 decrepit HP 41's I had acquired over the years. On first examination I determined they were only fit as parts machines. It was obvious that the prior owners were chasing a zebra strip problem with a soldering iron. However, I was lucky, and now all 5 are alive again, except for one bad keyboard on a CX.

But that does not mean they don't still have hidden flaws. Unfortunately I don't have a service or diagnostic ROM, and I would feel more comfortable if I could run those tests.

Hence my question.

Does anyone have a listing of the service or diagnostic ROM's.

I have loaded the MOD files in a virtual HP 41, but they are "takeover" ROM's so you cannot examine the subroutine code.

Am I naive to believe these are nothing but clever focal programs written by HP experts to exercise the HP 41 hardware?

Could these ROM's contain additional circuits needed for that purpose?

If they are just software, with a mechanism to autoload on startup and remap the keyboard, then it might be possible to extract the subroutines and publish them. Or perhaps there is already a listing somewhere that I haven't found.

I don't have the hardware (clonix, MDL etc.) to accomplish this task, but someone else might. In fact it may have already been done.

Anyone with the expertise to advise me on this project?
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01-08-2018, 05:59 PM
Post: #2
RE: HP 41 Diagnostic & Service ROM
(01-08-2018 05:47 PM)Don Williams Wrote:  Does anyone have a listing of the service or diagnostic ROM's.

I have loaded the MOD files in a virtual HP 41, but they are "takeover" ROM's so you cannot examine the subroutine code.

Am I naive to believe these are nothing but clever focal programs written by HP experts to exercise the HP 41 hardware?

Could these ROM's contain additional circuits needed for that purpose?

If they are just software, with a mechanism to autoload on startup and remap the keyboard, then it might be possible to extract the subroutines and publish them. Or perhaps there is already a listing somewhere that I haven't found.

I don't have the hardware (clonix, MDL etc.) to accomplish this task, but someone else might. In fact it may have already been done.

Anyone with the expertise to advise me on this project?

There are no source code for these ROMs around, only disassembly listings.

They are written in MCODE, not FOCAL/RPN. There is no special hardware, they are just wired to page 4 which makes them take over the calculator. Scans of the manuals are available.

You will need some Clonix or MLDL hardware to use these modules.

Håkan
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01-08-2018, 06:06 PM
Post: #3
RE: HP 41 Diagnostic & Service ROM
Thanks for the reply. Unfortunately it is not very encouraging. I had hopes not to have to reinvent that wheel.
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01-08-2018, 06:19 PM (This post was last modified: 01-08-2018 06:19 PM by hth.)
Post: #4
RE: HP 41 Diagnostic & Service ROM
I do not think there is a wheel to be reinvented, you just use these modules if you need them.

While the commented source code would be very interesting to see, these particular routines are probably of limited use outside of the diagnostics and educational field.

Håkan
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01-08-2018, 06:41 PM
Post: #5
RE: HP 41 Diagnostic & Service ROM
(01-08-2018 06:19 PM)hth Wrote:  I do not think there is a wheel to be reinvented, you just use these modules if you need them.

While the commented source code would be very interesting to see, these particular routines are probably of limited use outside of the diagnostics and educational field.

Håkan

I was envisioning reinventing routines that would duplicate exercising the hardware in somewhat the same fashion as the ROM's in question. I was an avid user of the HP 41 in the past, but I doubt I have the expertise to create those types of routines in question.

True. There is a very limited audience for these ROM's. Even I was only interested in them on this one occasion. Still. I think those subroutines (if they were available. Not.) would be an asset to the community.

Alas, it is not as simple as I had imagined.
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01-08-2018, 07:28 PM (This post was last modified: 01-08-2018 07:31 PM by Don Williams.)
Post: #6
RE: HP 41 Diagnostic & Service ROM
RTFM strikes again!

I have spent days researching this subject, and again and again I read that unlike all proceeding generations of HP calc's the 41 series lacks any BIT.

Does anyone know exactly what is occurring as far as BIT is concerned on a master clear?
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01-08-2018, 08:08 PM
Post: #7
RE: HP 41 Diagnostic & Service ROM
There is a step-by-step instruction in the Owner's Manual on how to power it up.

At master clear it clears memory, initialize memory system pointers and basic settings (flags and such). No hardware tests are performed.

The HP-41 does some simple memory integrity tests during normal operation, that are the only built-in tests available.

Håkan
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01-08-2018, 09:38 PM (This post was last modified: 01-08-2018 09:41 PM by Don Williams.)
Post: #8
RE: HP 41 Diagnostic & Service ROM
"Avid user" may be an over statement. I stayed within the bounds of focal programming and HPIL devices.

I guess I currently have a vague understanding of the procedures you are describing and it sounds like a promising adventure. I will probably be back in a few weeks with better questions.

Thanks for the info.
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01-09-2018, 01:07 AM
Post: #9
RE: HP 41 Diagnostic & Service ROM
Got the VASM. Got V41, which by the way doesn't seem to produce a trace.log file under win 10. Resurrected an old XP laptop and installed V41 on that.

I am currently perusing trace log files. Simple stuff like only turning the calc on and off. I recognize the memory checks on cold start but anything more complicated starts turning my brain into jelly, but I expected that.

This is going to go slow.
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