Re: Continuous Pulse-Width Measurement

On Sat, 23 Apr 2005 23:29:18 GMT, the renowned jawereq@xxxxxxxxxxx
wrote:

>Hi,
>
>I'm wondering if anyone knows of a microcontroller or some cheap hardware
>in combination with a micro that can be used to continuously measure and
>buffer all of the high and low pulse-widths of a binary signal. I'd like
>to be able to buffer about 1000 16-bit width measurements in one shot.
>
>The catch is that the smallest pulse width measurable needs to be 700ns or
>better (500ns would be nice). I've looked at using an input capture pin to
>a 20MHz or faster auto-cleared timer in combination with a DMA controller
>to transfer the captured pulse-widths to RAM, but all the transfer cycles
>generally add up to well over 1 micro-second. The 20MHz timer gives
>sufficient resolution, but the time to buffer the data is too long.
>
>Right now, the company I work for accomplishes this exact feat using an
>ASIC. Together, the current ASIC and micro cost about $7. Can the same be
>done for less money, and possibly with a single chip?
>
>I appreciate anyone's suggestions on this problem.
>
>Thanks!

If the total cycle time (ton + toff) can be guaranteed to be at least
some microseconds or longer you might be able to do it by using two
counter-timer modules in some micros, but otherwise I think you're
looking at programmable logic of some kind.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

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