Playing with HP2640B

Mattis Lind mattislind at
Tue Dec 5 09:02:38 CST 2017

I have now dumped the firmware from the HP2640B terminal. Since the EA4900
ROMs are not much like normal EPROMs in regards to pinout and supply
voltages I resorted to use a logic analyzer to dump the contents of the ROM
simply by parsing out the ROM accesses while the terminal did the selftest.
It took a quite many dumps to get the full firmware out of it since my
analyzer HP16550 boards have limited storage. Someone that has a HP16555A
board to sell?

One file for all four ROMs.

The good thing attaching the analyzer was that it helped me to find the two
bad 2102 chips on one of the memory boards. Now I get the full 5kKbytes.

While going through the HP2640B I found two boards which I cannot find
relevant schematic and description for, the 02640-60009 Display Memory
Access Module and the 02640-60088 Display Timing Module. Anyone has more
info on these?

With the firmware downloaded I tried to investigate why the small
Diagnostic Download example described here:
The example tries to call address 315 octal, but the firmware I dumped has
a HLT instruction at this location which explains why the terminal hangs

The HP2644 firmware is most likely different from the HP2640B firmware.

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