Not true Bob.

I have seen higher frequencies generated by paralell port.
Noone higher than 200 MHz though.  By bit-banging 8 bits paralell instead of
doing a normal write you can get 4 mbyte transfer over a paralell link if
you're lucky...

    KreAture

----- Original Message -----
From: "Bob Ammerman" <rammerman@ADELPHIA.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, January 22, 2003 5:56 PM
Subject: Re: oscilloscope pulse display


> 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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