I was digging in to my box of now very old PIC's and came
across some as of yet never-used PIC16c5A's.

	I need to convert the TTL output of an older PC's
parallel printer port to a serial data stream which will
ultimately be the DATA input pin on a RS-232 port on another PC.

	I know I will need a level shifter to get the +-12 volts
but my question is basically can the synchronous  serial device
in the 16C55a be made to behave like a UART?

	The parallel port on a PC sends an active-low strobe
pulse when the 8 data lines have a character on them and the data
are valid when the strobe goes back high.

	I would then want to squirt the data bits at an output
plus 1 stop bit and then send an ACK back to the PC.

	At that point, the PC strobes if there is a new character
and the whole process starts anew until there are no more to
send.

	I don't have any 16550A's but I do have these 16C55a's
which might work plus provide the logic to handle the strobe
catching and acknowledging and maybe even Busy signals.

	The PC will temporarily stop hammering the parallel port
if you bring Busy high.

	There are some other printer-specific pins such as On/Off
line and no paper indicators but I will probably just hard-wire
those to ground or a pull-up resistor, whatever they need to
work.

	My question is would I be better off buying a 16550A UART or
using the 16c55A PIC running at the right clock speed, of course?

	This is one of those impulse projects that I want to keep
simple because I didn't think I would need to do it but I
discovered that I do, in fact need to at least give it a try.

	Many thanks.

Martin McCormick WB5AGZ
--=20
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