This looks like a job for "Simple Pic".  Just program one to put out the
signal and be controlled by the parallel port of the pc.  Even simpler, use
something from the other device or even have it to supply power to the pic
to start the oscillator, or in conjunction with the parallel port.

Instead of the parallel port, the serial port could be used to turn pic on
and off.  use the timing of the pulse width when sending a hex 80 and a hex
FF to signal the pic to start /stop oscillator.   Wouldn't need a fancy
RS232 interface on pic, just look at the data pulse and measure time for
control.

Bill

----- Original Message ----- 
From: "Herbert Graf" <mailinglist2@farcite.net>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, October 19, 2005 12:42 PM
Subject: Re: [EE]: Could PC Parallel port drive a device that needs
TTLtriggers?


> On Wed, 2005-10-19 at 11:45 -0700, John Waters wrote:
> > Hi All,
> >
> > I have a equipment whose operation invloves being triggered by a
continuous
> > pulse train of 1 Hz at TTL level. Currently I'm using a funtion
generator
> > with TTL o/p for doing that, but I want the operation be more automatic,
so
> > I'm considering using the parallel port of a PC to replace the function
> > generator. However I wonder if the parallel port of a PC is TTL
compatible.
> > Could anyone give some comments?
>
> Most are TTL compatible. Some will only be 3.3V (i.e. laptops), which
> might still work fine with TTL hardware, but I wouldn't count on that.
>
> A bigger problem is how accurate do you need that 1Hz to be. If you're
> running just DOS you can get it pretty close, but in Windows expect that
> 1Hz to glitch every once in a while.
>
> TTYL
>
> -----------------------------
> Herbert's PIC Stuff:
> http://repatch.dyndns.org:8383/pic_stuff/
>
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