Re: Plus/4 RS232 woes

From: Mia Magnusson <mia_at_plea.se>
Date: Wed, 5 Sep 2018 19:34:34 +0200
Message-ID: <20180905193434.00001199@plea.se>
Den Wed, 5 Sep 2018 09:47:16 -0500 skrev Jim Brain <brain@jbrain.com>:
> The direction of the RxC pin is set via bit 4 of the control
> register. if 0, RxC is an input, and is used to drive the receiver
> logic.  If 1, it is an output and will represent the output of the
> divisor above (16* the receiver bps rate)
> 
> The idea was to allow split bps rates (600bps send, 300bps receive).
> No one actually used it, but it is supported.

There might also had been an idea to use it with for example a Kansas
City compatible tape interface.

The various schematics of Kansas City compatible interfaces I've seen
does of course just modulate the transmit data signal, but from the
audio signal it generates both the receive data signal and also the
receive clock. This way it works even when the tape speed varies quite
a bit, as you would expect from cheap portable mono audio cassette
recorders.

It's a rather inefficient standard as it stores a start bit and a stop
bit for each byte and afaik it was also usually used to store data as
ascii and not binary. In comparison the PET tape interface performed
rather well.

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Received on 2018-09-05 20:00:05

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