Or simply an external (16bit) counter that is "gated"
by the "pulse". On the falling edge of the pulse, an 
interrupt is generated and the 16bit counter, the
analog lines and the encoder is read.

Now, there are a lot of factors missing, such as the
allowed delay from the falling edge of the pulse until
all analog lines and the encoder has to be read, just to
mention one thing...

Regards,
Jan-Erik.

> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu]On Behalf
> Of Martin K
> Sent: den 1 augusti 2006 00:41
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC]: Newbie questions on external timers
> 
> 
> 80Mhz is pretty fast for a PIC.
> Perhaps you would need to use a PLD or FPGA?
> --
> Martin K
> 
> Les Elkins wrote:
> > Hi folks,
> >
> > I'm a new person to pics. By background I'm a software guy 
> with a smattering
> > of hardware many years ago. Lately I've been tasked to look 
> for alternatives
> > to a data capture board. We think we can make something 
> cheaper and much
> > better than what we have.
> >
> > The gadget I have to interface with has the following traits:
> > 	-A pulse-width-modulated signal coming out at 80MHz
> > 	-Three analog lines
> > 	-An encoder on a spinning wheel.
> >
> > The pulse signals come along at up to about 5KHz. When a 
> pulse happens, I
> > need to 
> > 	-Grab the width, measured with an 80MHz clock
> > 	-Grab the three analog values
> > 	-Grab the encoder value
> >
> > This data must be buffered and streamed out to a host.
> >
> > I've been reading data sheets and it seems a 
> dsPIC33FJ128MC710 might be a
> > decent choice: Quadrature encoder, decent amount of RAM to 
> buffer stored
> > data, and enough A/D to easily get the analog data. 
> >
> > However, it's only running at 40 MIPS, and my signal is 
> 80MHz. As I'm
> > reading the data sheets, I see reference to running the 
> Type A Timer in
> > asynchronous mode from an external source. I haven't found 
> anything that
> > tells me if this external source can be 2x the CPU clock speed.
> >
> > So.... Can someone tell if this is a valid approach (or 
> tell me which
> > documentation I should be reading to determine that)? If 
> this won't work I
> > assume I could add an external timer- would this be a 
> reasonable approach
> > for this soft of signal?
> >
> > My hope is to demonstrate the validity of this approach using the
> > downloadable Microchip tools. If that works I can get an 
> electronics type
> > with appropriate hardware background to support me in this 
project.
> >
> > It's been quite a while since I looked at PICs for any projects. 
I'm
> > impressed with what's out there and the clock speeds- my 
> last glance into
> > this area only low-speed chips were available.
> >
> > Thanks,
> >
> > Les Elkins
> >
> >
> > Les Elkins
> > Spatial Integrated Systems, Inc.
> > Rockville, MD
> > www.sisinc.org 
> > les.elkins@sisinc.org
> > 301 610 7965 x107
> >
> >
> >
> >   
> -- 
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> http://mailman.mit.edu/mailman/listinfo/piclist
> 



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