Difference in CX roms?


My co-worker has a halfnut (rounded corner) CX, mine is the older type. On mine, typing shift-ON causes the clock to be displayed, but not on his.
Is this just a flag setting? Or are they different in the ROM encoding?


I have a half-nut 41CX here, and shift-On works exactly as expected. I don't know of any flag that affects this, nor any ROM differences. My initial response is that his unit may be faulty.


--- Les [http://www.lesbell.com.au]



this sounds bad... Bad contact, bad environment, bad feelings. Any CX, AFAIK, calls the clock when [SHIFT][ON] is pressed. I do not remember seeing any flag that would suppress or override this feature.

In any case, if there is no trouble, try a [MEMORY LOST] procedure and call the clock with [SHIFT][ON]: all flags should be reset to default values and it must work after that.

If your co-worker is sure it's not an ordinary CV with X-Functions and Time module built inside, I'd be suspicious about it.

Also, try [CAT][2] and see if it behaves like the HP41CX [CAT][2]: only headers must be shown instead of all available function for each attached ROM.

Going further, try [XEQ][ALPHA] ED [ALPHA]. If this results in [NONEXISTENT], this is not an HP41CX.

Success. And let us know what happens.

Luiz (Brazil)


The 41CX manual describes Shift-On as being like switching the calculator off, then on before displaying the clock (which is why it has an effect on flags 12 through 20). However, [XEQ] CLOCK does not do this.

So, you might gain an insight by investigating whether [XEQ] CLOCK behaves the same way.


--- Les [http://www.lesbell.com.au]


Hi, Les Bell;

after reading your post I thought about another possibility, too. A few days ago I found a weird problem: one HP41 did not switch to ON. The LCD flashed the 0.0000 and vanished fast. I tried another battery set with a different holder and it worked fine. But its battery set and holder showed the same problem in two other calculators. I decided to measure batteries voltage while switching the calculator ON, and I found an weird behavior. Battery voltage was O.K. with calculator OFF. When ON was pressed, voltage dropped to less than 2 Vcc and the calculator could not switch to ON. I measured each battery and voltage was O.K. in all of them. I decided to load each of them and measure current intensity. There it was: one of them was not able to reach 1 mA. I replaced it and tested current intensity when the calculator is switched to ON: has a peak that goes beyond the steady maximum current (program running or key pressed). I have no precision instruments (not yet) to measure this current peak, but I'll find a way to measure it soon.

Based on this and after reading your post, I think this possibility should also be taken into account. If BAT indicator is present, I'd also suggest trying with a new set of batteries. Who knows?

Best regards.

Luiz (Brazil)


Hi Les Bell, Sean, folks;

I had a look at the HP41CX Owner's Manual, Vol. II, and found something in p. 383.

If the batteries are low, either CLOCK or [SHIFT][ON] will turn the "computer" to OFF. The fact is that the low battery condition may also be "sensed" when the calculator is switched to ON but this condition does not prevail, what would gives us a low battery condition without BAT annunciator. I'd still suggest testing the unit with a fresh battery set. Just in case...


Luiz (Brazil)

Edited: 23 July 2003, 2:09 a.m.


OK - that's it.
1) I KNOW it's a CX (Used ED on it, saw the "CX" on the case), and
2) I KNOW the battery was low.

You guys figure EVERYTHING out!


Hi, Luiz:

By George - I think you've got it!


--- Les [http://www.lesbell.com.au]


Low Batteries are usually the cause for this beaviour. You can easily see why:

Most 41s (all I have ever held in my hands, anyway) produce an audible sound when the CPU is running. Just program an eternal loop and start it, then hold your ear at the back label - you will hear a low hissing noise. Press R/S to stop the program, and it's gone.

When you press [SHIFT] + [ON], you will hear the CPU run as it turns the calc off, then back on. After that, the CPU will run until it's time for the first display update. That is, in CLKTD mode, where seconds are not displayed, the CPU will run continuously for up to 1 minute, until it's time to turn the minutes. After that, the 41 sets an internal timer, and the CPU will turn off until it's time to update the diplay again. Do this in CLKT mode, and you will hear the CPU quickly turn on and off every second after the initial continuous period is over.

As this can use quite some battery power, it's easily possible that you see no BAT indicator, but the clock will still not turn on. Same with the Card Reader, BTW.

Besides that, I remember reading somewhere that the 41 knows at least two different low power levels, and obviously only one can be communicated via the BAT indicator. Don't know which one, however.


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