|Re: How was this PPC-ROM made?|
Message #3 Posted by Chris Catotti (Florida) on 30 Sept 2002, 11:36 a.m.,
in response to message #2 by Chris Catotti (Florida)
How do you make a module for the HP-41?
Hear are some thoughts/history. Please correct my mistakes ...
I think someone copied the PPC ROM into a package as described above.
That I know of there were four ways to copy an HP-41 ROM and actually use that copy on an HP-41:
1. Copy it into HEPAX RAM. The HEPAX (HEwlett PAckard eXpansion module) contained 8K or 16K RAM and a ROM that allowed copying a RO<M into its RAM. The RAM is volatile (lost when module is unplugged from calculator, but not cleared by MEMORY LOST on HP-41). The existance of this possibility is not real useful ... the HEPAX is relativrely rare and the last one on ebay exceeded $500
2. A RAM or EPROM Box. Much bigger than a module, but it works, some vintage ones exist, and some smart hobbyists are still making their own.
3. Zengrange ROMs. One-time programmable using a fusible link ROM. New, everything is "1" inside it, once you "burn" a "0" it remains a zero (open-circuit for that bit) forever. There was a low-voltage burner that could plug into a port on the HP-41, and with a ZENROM or CCD module, you could make your own ROM.
4. UV-EPROMs. These were programmable with some king of EPROM burner, and offered the ability to make multiple copies of ROMs. The good news is they can be erased with an ultraviolet light. It requires a significant amount of hardware to program them. I hope to learn more. EPROM modules, I think were made by CMT (described in one of the last PPC journals) with 8KB, so two pages fit into it. For example, CCD Version B modules were made from the same EPROM modules, or the SKWID INK Barcode Module."
I am not aware of anyone producing items 2, 3 or 4.