the HP9816-(HP9000/216)-keyboard is definitively not HP-HIL-type.
But the original HP150 wasn't HP-HIL either. It was a shift-register-sort
of interface similar in concept to the HP9000/216, but different in the
Onthe other hand, both the HP150-II and the HP9000/217 (HP9817) use
HP-HIL is a bi-directional-bus-poll type protocol,
HP9816 is unidirectional synchronous "long shift register" type.
Here is a raw diagram of the keyboard protocol and connector
'My' scrematics fotr the HP9816 should be on http://www.hpmuseum.net/
They include the 'compact' keyoard scheamtic, and it's very easy to
deduce the interface from that.
One curious thing about that compact keyboard is that the switches do not
form a scanned matrix like in most other keyboards. Instead, one side of
each swithc is grounded, the others go to a bank of 4051 (!) multiplexer
chips which select the keys (and the counter fro the twiddleknob) in turn.
There exists an protocol converter from the HP9816-keyboard to PS2
PS2 to HP9816 should be possible as well.
The reverse (PC keyboard to hp9816 host) would seem to be more useful,
given that some plastic bits in the HP keyoards are failing. Fortunately
the same keyswitch design was used by other manufacturers, so it's
possible to raid parts (my 9816 has plungers raided from a spare VT52
keyoard, even the left shift key came from there. It looks wrong, of
course, but it's the right footprint, so it fitted with no modification
and if I ever find the right keycap I can fit it).