The HP 9403A odyssey might be close to an end. After tracing most connections on the "DVS Program I/O" connector to corresponding ICs, thus understanding if they are inputs or outputs (they all end up into an HP 1820-0107 level adapter), I begun to take control of the device:
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| HP 9403A: first signs of human control after 40 years. |
I know which are control lines and which are data lines. There is no serial protocol, but just plain parallel negative logic. If I want to do something with the bulky piece of equipment I will need a microcontroller with lots of I/O lines, or some serial-to-parallel (open collector) converter.
