HP 42S ROM-versions


Inspired by Nelson M. Sicuro's post I downloaded emu42 and wanna play with it now.

But now I am not sure wich calculator to use for downloading the ROM.

I have only one 42S, but my dad has another few, I don't have the serial-numbers here though.

Now my question is, what are the diffrent rom versions, where are the diffrences and, how to find out wich Calculator has wich ROM?




I found somewhere the information to get ROM version:
Enter in "test" mode pressing ON and LOG together; then press <- (back arrow) to start the debugger; it will point to a routine that shows the ROM version on screen pressing the decimal point (execute, from the debug). Mine shows in the left "A" and in the right "5". To exit press ON together with SQRT (square root).






More details http://www.finseth.com/~fin/hpdata/hp42s.html


For the HP42S the ROM Rev. A, B and C are existing.

In the version screen the character on top left side is the version, the number on top right seem to be the reason of last calculator restart.

On the emulators all three ROM versions have the COMP bug, because this is hardware dependent. Early HP42S with ROM rev. A use an older revision of the 1LR2 Lewis chipset with a bug inside that the COMP bug don't occur. I personally have a late HP42S with ROM rev. A SerNo. 3017Sxxxxx _with_ the COMP bug.

IMHO use the latest Rev. C ROM, the version I use for the Emu42 development.



Thank you Christoph. I hope it works. The HP42 is at home and I will try that at the weekend.

Your HP28 emulator seams to be interesting too, does it run with either a 28C or a 28S rom-image?




Only with a HP28C image. The HP28S hardware is more similar to the HP42S, because they use the same chipset.

More about this in http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=313 and http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=275.


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