MCODE: The insidious AECrom


A favorite of mine is the AECrom, due to its excellent curve fitting engine (CRVF) and some other goodies. But, the AECrom is a strange beast - when used together with my NoV-32, it occasionally locks the calc when I turn it ON. This only happens with the AECrom. My suspicion is a conflict at start-up as the AECrom does funky business if you press and hold the ON key (it switches its modes between inches, degrees etc).

As the original AECrom is in conflict with the NoV-32, I decided to copy the rom (with the COPYROM command) from page #E to page #A (I already disconnected pages #A and #B from the HEPAX chain as explained in the HEPAX manual. I use page #B for my own MCODE rom project).

Now strange things have occured: Cat 2 displays strange symbols instead of the anticipated AECROM, but if I press ENTER right there, I do get the functions inside the AECrom. But after such a CAT 2 the calc goes apeshit (locks, funny characters, high pitched sound on key press etc). Trying to access the functions, I get interesting messages like AECROM-32 (seems like an error message). I have cleared the polling addresses after copying the rom, so it doesn't lock the calc when I turn it on anymore (now, that's the good news), but I'd like to repair the newly copied beastie-rom so that it becomes my favorite AECrom residing nicely in my NoV-32 ram.

Any takers?


Hi Geir,

Seems it's on my side of the fence... ;-)

I've tested with my own AECROM (the real thing, not an image into Clonix) and have found no such troubles. Here is my config on a CX:

Port 1: NoVRAM (no ROM images burnt into extra pages)

. HEPAX emulation loads itself at page #6 (as expected)

. Page #8 HEPAX RAM

. Page #9 Custom ROM image (I'm on TLC with M-Code for beginners... :-)

. Page #A David-2C (a very positive side effect of fixing the WROM bug!)

. Page #B Labels (unvaluable with MF entry points!)

Ports 2 @ 3: Empty

Port 4: AECROM.

Calc turns ON/OFF as suppossed. Holding ON while in standby, makes AECROM loops through its different options. Releasing ON sets the last displayed option as default.

None of the above causes any crash, nor any other irregular behaviour.

I've just placed the promised SW updates on my web page a few minutes ago. Please download it and upgrade yours, as there are chances that the latest mods make it run quite more smoothly.

Best wishes from Spain.



I will download and test.

My AECrom config only does the weired dance once in a while. It's never been consistent. It can go for weeks and behave properly and then it gets its fits again.

You know what's up with the strange COPYROM - that it seem to not copy the rom properly?



Can you please run a small test for me?

Burn your NoV-32 as a CX service module in a Clonix-like fashion using the ServiceX.HEX from my web site.

Plug it into port 1 (make sure no other ROM's are plugged in.)

Turn your calc ON and press "1" unpon [SELECT TEST] display.

Take down the speed of your HP-41CX.

I have not been able to test NoV-32 with CX above 374kHz (as this is the fastest CX unit I have) and I'm aware of units slightly above the 380KHz limit.

It will be good to discard the CPU speed as a potential source of trouble.

With the new RAM2ROM1.HEX it should be easy to find out if the COPYROM have done its job properly:

Once the ROM has been copied into RAM, dump a copy of it by writing the corresponding control word into H'4100 (see details here).

Then, extract the .ROM file from your NoV thru the serial programmer.

At this point you can compare the .ROM file with the "original" image of said ROM pack and point out the differences if any.

Please note, the new version of NoV-32 activates RAM chip 0 on power ON instead of chip 1. The RAM contents is of course preserved and can be accessed as usual by writing H'001 into H'4100.

Best wishes and keep me informed.


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