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HP 41: Creating EPROM Images - Printable Version

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HP 41: Creating EPROM Images - Michael Fehlhammer - 05-30-2018 01:18 AM

Vintage EPROM devices ( like HHP portable EPROM, ERAMCO EPROM box etc. ) use standard EPROM chips and spread the 10-bit words of HP-41 mcode over two chips.
The usual distribution is: one EPROM chip holds the lower 8 bits of all words (mostly called L8), and the other one holds the two most significant bits (U2), in a packed format (4x U2 in one byte).
For example an HHP Portable EPROM in 32k (8 pages) configuration holds 8 times 4k byte (L8) in one 27256-type EPROM (256 kbit), and 8 times 4k x 2bit in one 2764-type EPROM (64kbit).

Now I'd like to burn my own selection of ROM images onto my HHP EPROM device.

For that I need a program that creates these two files (L8 and U2) from a standard HP-41 ROM image ( 16 bit, 6 leading zeroes); since I am pretty sure that such a tool already exists and it's stupid to reinvent the wheel, I hope that some HP-41 expert could give me hint where to find the conversion utility.

RE: HP 41: Creating EPROM Images - Didier Lachieze - 05-30-2018 09:12 AM

You can use HIGHLOW.EXE or EPROM.EXE which are part of SDS II.
Or you can use the program GOINTEL.BAS that has been published in the article “Programming EPROMS for the HP-41” published in HPX Exchange V1N3.
Both are available on TOS.

Here is an interesting chart showing the different ways to program EPROMs. The source web page where I found this chart is not available anymore.

RE: HP 41: Creating EPROM Images - MeindertKuipers - 05-30-2018 09:14 AM

I have a very old Turbo Pascal program that does the reverse, buy never took a ROM file apart in L8 and U2. Never attempted to runs this on a modern machine.
Let me know if you are interested in the source

RE: HP 41: Creating EPROM Images - Michael Fehlhammer - 05-30-2018 11:53 AM

Hello Didier, hello Meindert,

thank you for your valuable tips!
I am going to download the mentioned programs and try them out.

@Meindert: Currently I have no need to do the reverse (create a .rom file from L8 and U2), but should I run across an EPROM with unknown content, it would be nice to share it as a rom file (or upload it onto a 41CL). Therefore I am interested in your Pascal source.
Please send it to my private email; thanks!