HP 42S what can we do with a 2nd rom?


I know it has been exposed sometimes the fact that 17BII international units have 2 roms in it.

1st Rom ( calc Rom ) 2nd Rom ( Language Rom ).

The question I have is if it would be possible to access to a 2nd ROM? XFCN is the key??

So If it was possible what type of ROM could it be? only acces ROM or a substitute of the Original ROM??

Would it be a way to expand the 42S as the 41 series with its rom Modules?



I don't think there is a lack of interest in this question, just a lack of knowledge. Without some inside information, it's probably impossible to utilize the second ROM.


There were threads about this topic in the past.

To sum them up somehow:

It would be possible to utilize the language ROM space for OS extensions,

but you had to find someone who actually knows how to program the functions, which I guess are only a handful of people,

and someone to burn and wire a suitable ROM/EPROM chip to the location.

The first problem is a rather time-consuming one,

and in combination with the 2nd problem (hardware mod) a rather expensive one.

There may be many people wanting to have and extended HP-42S, maybe with an XFCN ROM

maybe with I/O capability (which works, as Christoph Giesselink demonstrated),

but there are only a few who even let their HP-42S upgrade to 32K RAM,

and maybe not enough people to pay off the effort for making the real h/w extensions, like XFCN ROM and I/O;-)





May be a little too late, but I for one, have built the HW mods in order to create a "Frankens-42-MLDL" with access to the memory bus.

Regrettably I'm on the lowest end on Saturn assembly knowlegde, but since I met Mr. Giesselink at last Alshwill meeting on Nov. '08 I find an interesting field for experiment and development... although (as Raymond has pointed out), most users won't let their valued and valuable 42's in foreing hands under no circumstances. Which turns all this in a project of myown in the long term.

My interest is, by one hand, simply knowledge; and by the other hand, if I only could get...

- a way to create 42's RAM back-ups (may be IR input?)
- PC connectivity (serial or serial converted to USB externally)
- a real time clock functions set, as those in the TIME module of the 41

... then I may try a 128KRAM upgrade also.... ;-))

Oh, well, it's real late here in the Canaries, may be I'm just dreaming.

Best wishes.


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