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
>
>
>
>   
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist