Actually it will NOT be all that fast. In order to ensure compatibility with
old hardware access to physical ports like the parallel port is slooooowed
waaaaay dooooown by the chipset. You will typically see signals in the 1MHz
range or so.

Also, most parallel ports have rise time control to reduce EMI, and you have
to account fro that.

Finally, the same hardware that slows down access to the port introduces an
amazing amount of jitter to the signal. So instead of getting a clean
1MHzish signal you'll get what almost looks like random edges.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Kyrre Aalerud" <kreature@C2I.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, January 22, 2003 11:45 AM
Subject: Re: oscilloscope pulse display


> It will be very fast indeed on a 1.1 GHz computer.
> Depending on what other tasks the computer is doing at the same time, and
> depending on how you are switching the pin, it may wery well be at 500
MHz.
> It will also depend on the hardware of the PC.  If it can handle what you
> are forcing it to do.
>
>     KreAture
>
>
> ----- Original Message -----
> From: "rad0" <rad0@ATTBI.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Wednesday, January 22, 2003 5:27 PM
> Subject: [ee]: oscilloscope pulse display
>
>
> > OK, you guys talked me into getting an oscilloscope
> > and now ii's displaying something that is wierd
> >
> > I have a program that toggles a pin on the parallel port of a PC
> > just on then off, as fast as the thing will go
> >
> > and this produces a display of a horizontal thick line with
> > a completely vertical line, spike, every so often, I've forgotten
> > to record the time between these vertical spikes or lines
> >
> > Is it possible that this is just going too fast for the oscilloscope? a
> > 100Mhz
> > the PC is a 1.1 Ghz
> >
> > I was expecting a square wave of sorts, and this thing I'm not sure what
> it
> > is...
> >
> >
> > the thing works fine on pic pulses, giving nice square waves for the
range
> > of
> > pulses given by a 20mhz pic
> >
> >
> >
> > thanks for any insights
> >
> > --
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