Analog modem emulator?

[Tony Duell]

> > Yes. The bit-banger is fairly usless for serial input, although it's fine 
> > for output. I suspect it was mainly used for driving a serial printer (I 
> 
> Can someone clarify what "bit-banger" means and why it was different from a 
> contemporary serial interface card?

'Bit banging' is a common term for doing the serial<->parallel conversion 
in software (using shift instructions, etc) rather than using a hardware 
UART (or ACIA, etc) chip. It doesn't necessarily only refer to RS232 
interfaces, it's quite common to say something like "I'm bit-banging the 
I2C protocoi on a couple of the port A pins of that PIC".

The bit-banger that I refered to here is whichever of the Apple cards 
didn't use a UART chip. There seem to be 2 approximately contemporary 
cards, and I am sure to get them the wrong way round, but here goes : 

The Serial Interface, which contained a few TTL chips, and a couple of 
PROMs. This is the one I call the bit-banger

The Coommunication card which contains a 6850 ACIA (similar to a UART).

-tony