Bit Banger was Analog modem emulator?

[Brent Hilpert]

Tony Duell wrote:
> I have never seen a bit-banged RS232 (or current loop) port on a
> minicomputer. Anyone know of one?

The HP 2116, 2115, 2114 minis (1966-70) used bit-banged serial.
In addition to bit-banging for a single device, there was an I/O interface
for handling up to 16 terminals via bit-banging, the interface being - in
essence - merely a 16-bit parallel port with each terminal assigned to one of
the 16 I/O bits. This was used by the 2000A timeshared BASIC system.

(Between bit-banged I/O for multiple terminals, interpreting the BASIC programs
and timesharing overhead, it's amazing the processor found any time to do
anything 'useful'.)