Programming CMT EPROM modules for HP-41


I have succeeded in programming one of the subject modules and it turns out it is pretty straight forward. The pads that the PLCC package EPROM are soldered down to, are actually vias that go through the board to corresponding pads on the under side and all that is required to program them is to make connections from these pads to a standard EPROM programmer. I made up a connector using pogo pins that have their sockets anchored between two layers of 0.05" pitch perfboard that I got from Digi-Key. I mapped the contacts to a "standard" 28 pin dip connector and was able to read and program the EPROM using my ancient Xeltek Superpro II. There may be problems with some programmers because there are resistors on the module that pull down the CE and OE pins so when powered on all the outputs are active and at least one of my EPROM programmers did not like this.

One thing to watch out for is it would seem that the commonly available images of ROM modules the 10 bit HP41 words are split into two byte with the byte containing the 2 MSB first and then the next byte contains the lower 8 bits, this is the opposite of how the CMT modules want the data arranged, they want the lower 8 bits first. I reversed the bytes by splitting the image, writing alternate bytes to two files and then merging the two files to get the correct byte order.


Hello, I'm interested as I have one 16K CMT module that is currently unused, it just contains the CMTTST program.
Running CMTTST with module plugged in port 3 gives:

16K PT3 OK

Would you consider providing programming services for these modules? Or can you share more details about your hardware design?

Edited: 21 Jan 2013, 4:26 a.m.


I could provide programming service for a small fee, but I will also post my design once I decide on a good way to align the module and hold it against the pogo pins.



this is how the original CMT EPROM adapter looks like.



Edited: 22 Jan 2013, 5:47 p.m.


Thanks for the pictures that is much clearer all I had seen before was tiny pictures, unfortunately I don't think I can reproduce the clamping mechanism they used.

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