Bit Banger was Analog modem emulator?

[Tony Duell]

> 
> An early example of a bit banger serial interface was the Motorola 6800
> MIKBUG Monitor ROM. It used a parallel interface chip (MC6820 PIA) as a


The earliest desktop comuter I know of with a bit-banged serial port is 
the HP9830.

There were 2 serial interfaces for that machine, I'll probably get the 
model numbers wrong, but here goes.

The 11205 was a hardware serial interface, using TTL shift registers, 
etc. You set the baud rate in hardware (links or switches on the PCB), 
the 'computer side' of the interface looked much the same as the other 
interfaces for the 98x0 series, it was commonly used to link up serial 
peripherals, printers, etc.

The 11206 was a bit-banger. It worked with a terminal emulator ROM which 
turned the 9830 + 9866 into a printing terminal with local storage (in 
the BASIC program area of the 9830's memory, which could then be saved on 
cassette and loaded back again). The baudf rate was set by a keyboard 
command, anything from 3 to 440 baud IIRC (strange limits, those...)

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

-tony