Analog modem emulator?

Dwight K. Elvey dwight.elvey at
Mon Aug 15 14:11:39 CDT 2005

>From: "Jim Leonard" <trixter at>
>Tony Duell wrote:
>>>>Sounds like the cards were approximately contemporary.
>>>That's perfectly reasonable.  It could be that the Serial card was meant
>>>for local interfacing to serial peripherals while the Communications card
>>>was meant for "high-speed" telecommunications applications.
>> 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?

Hi Jim
 Bit-banging usually means that there is no uart or even a shift
register. There is a single bit port that the data is directly
sent from the main processor. It requires that the processor
produce all the bit timing. Things like clock interrupts
or variable refresh would be bad( with the exception that the
clock interrupt could be the timing for a fast processor ).

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