[GreenKeys] Keyboards - 32/33 and Compact 28 KSR

[Harold Hallikainen]

As I recall from reading the datasheet on that keyboard, it had an
interesting interface.

It appears the keyboard was all mechanical. I suspect there were code bars
under the keys, like in the model 15, that opened or closed switches for
each bit. Once a key was pressed, it, or at least the code bars, were
locked in place and another switch closed indicating the character was
ready. The computer detected the "character ready" signal, captured the
character from the code switches, then sent a pulse to release the lock on
the key so the next key could be pressed. I suspect this pulse also
released the character ready switch so the computer would not repeatedly
capture the same key.

As I recall from reading the datasheet, the interface was parallel, as
described above. It's interesting that they did not just stick a motor on
a model 15 keyboard and use a serial interface.

Harold