HP-71b CMT-64E Eprom - Whats under the black goop ?

[J-F Garnier]

(03-18-2020 01:49 PM)Dave Frederickson Wrote:  I figured an external programmer was used because the card reader port can't provide the necessary programming voltage. I was more curious about how to create the EPROM image for the programmer. It sounds like all it takes is to dump an image from a 71, invert all the bits using one of the many tools available for manipulating EPROM images, and burn the chip and see what happens.

The HP71 doesn't provide programming voltages to any port; the CMT front-port EPROM modules are programmed by being plugged into the CMT programmer, which DOES provide the programming voltage.

To make the ROM image from a IRAM port, I recommend to use the ROMCOPY function to first create a ROM file on a mass-storage unit, then to load it back (again with ROMCOPY).
This may not be needed for ROMs with only LEX files, but it is mandatory for ROMs that include BASIC files, to make sure the chaining/compilation process is correctly done. This is something we discussed in the past, but I can't find the reference right now.
Then, a small program can PEEK into the IRAM port and send the bytes (complemented) to an external programmer.

J-F