Diacom plus on Pentium laptops

[Ken Kelly]

Dave,
	Actually a Uart will work fine if you can get within 3% of
the desired frequency, and a modern Uart can do the 8160,
and 160 hertz rates within the 3%. The issues with Diacom
not using the serial port are:

	1) The ALDL voltages are 0 to 5 Volts or 0 to 12 volts.
RS-232 voltage spec is -10 to +10. So voltage level
converters and a negitive voltage power supply would be
needed.

	2) The diacom needs several control leads to switch the
Control resistors, etc. They found it easy to use the 8 data
bits on the parallel port for this.

	Certainly a dedicated interface box to do the level
shifting and control function feeding to the UART would have
been a more elegant & robust solution, but it would have
been more expensive.

		Ken

Dave Williams wrote:
> 
> -> Am I illiterate here on the latest and greatest?  I somehow thought
> -> that UART's solved that problem long ago....?    GENE
> 
>  The UARTs used in IBM-compatible PCs are "smart", that is, they do a
> lot of processing in firmware that other machines did in software.  The
> penalty for this is the UARTs can only "see" data rates that match their
> firmware, much like the story about frogs only being able to distinguish
> between "fly" and "not-fly".
> 
>  You can't program the UART to "see" an ALDL stream, so you plug the
> cable into the parallel port and poll the hell out of it to see what's
> going on.  But there are many types of "standard" parallel port, plus
> the occasional wildcard from various OEMs, just to make the life of the
> programmer even more difficult.
> 
> ==dave.williams at chaos.lrk.ar.us======================================
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