Portable EPROM device and CMOS EPROMS

[steve]

I have an HHP Portable EPROM thingy for my HP41. It is inside a cardreader case.

It contains 2 EPROMS, a 27128 and a 2732 (actually an HN4827128G-30 and an HN482732G)

Questions:

0) can it use other rom types (I've seen references to using a 2732 and a 2716, so I was surprised to see a 27128 and a 2732, although the relationship fits the 10 bit word of the HP41)

1) could I use CMOS eproms (e.g. 27C32)

2) what do the DIP switches do inside this device?

3) does anyone have a manual for it?

4) Can anyone point me in the direction of documentation about putting code in these EPROMS (I have access to eprom burning equipment, and I plan on trying to reverse engineer these roms, but I'd _FAR_ prefer not having to do all of this through trial and error.

5) there's got to be an easier way of opening and closing these card reader cases. It takes me forever to get it shut again...

(I have a ZEN ROM coming to me in the mail, and I believe it's manual explains some of this stuff??? Any confirmation of this wouls also be appreciated.)

[Dan Grelinger]

I can be of very little help, since I don't have one of these. The other custom memory devices that I have seen use dip switches to control read enabling, and addressing of the roms. I believe that this device allows rom to be addressed anywhere within the HP-41's 64K memory space, even in page 4, the diagnostic rom space.

The ZENROM manual will help you with the HP-41 internals, including memory usage and utilities to examine ROM. However, I don't think that there will be any help with this EPROM device.

[steve]

I've taken the opportunity to have a friend with an EEPROM programmer to read the EEPROMS.

I can identify what looks like the programs in the larger ROM image (All I've done at the moment is look at it in a hex editor and I have seen all of the global labels)

In addition to the stuff that appears in CAT 2 (which are all normal HP41 programs (i.e. not microcoded functions) there appears to be a dump of the X-Functions module (some names in there seem rather familiar...).

The smaller EPROM (I gather) is used for the other 2 bits of the 10 bit microcode instructions. I cannot make head ot tail out of what's in it (I'm not surprised).

Is there anyone out there who could take a look at these ROM images and tell me more about them?

[Dan Grelinger]

The best way to look at these EPROMS is with the ZENROM "MCED" function, or with it's disassembler. It can interpret all ten bits at once, rather than trying to make sense out of the first two bits and the remaining 8 bits separately. In machine code, the leading two bits are very important to the instruction. In user code, they play a small role in allowing the -41 to keep track of the first byte of a multiple byte instruction. Ever notice out the HP-41 backsteps much faster in ROM than in RAM? That is why.

[steve]

How clever!

I'm looking more and more toward getting that Zenrom...

[steve]

I've now had the ZenROM for a week or so. I have decoded how the information is stored in the EPROMS in my EPROM device (although I'm not exactly sure what the DIP switches inside do),

The ZenROM is GREAT!!!!!

If I could just get a Q-Rom device of some sort....