Re: The Perfect Counter/Timer Circuit?
- From: Andy Sinclair <me@xxxxxxxxxxx>
- Date: Tue, 12 Jul 2005 09:15:02 +0100
Robert Scott wrote:
>I?m looking for just the right counter/timer module to perform a very
>specific task. I have a quadrature encoder turned by an engine
>crankshaft. The encoder has the usual A-phase, B-phase and Index
>outputs. With respect to the encoder?s Index pulse, the count of
>A-phase pulses defines various angles of the crankshaft. I need to
>generate signals where each transition is individually programmed to
>occur at a specific crankshaft angle. Two consecutive output
>transitions will always be far enough apart so that firmware can
>intervene to set up the next transition. This seems to call for the
>output compare function as supported by a number of microcontrollers.
>But I also want an automatic reset of the counter by the Index pulse.
>Which counter/timer devices have both and output compare function and
>an external counter reset function? The output compares in the
>Microchip family don?t seem to have the automatic reset function. I
>am open to both counter/timers as part of microcontrollers or
>independent devices such as the 9513 chip. (But I have examined all 24
>operating modes of the 9513, and none of them will do the job.) The
>encoder pulses at their fastest are 2 usec. apart.
As Andreas mentioned, a TPU equipped microcontroller would be ideal
for this task. If you write a custom microcode function you can even
configure multiple transitions in one go.
What other requirements do you have for the application?
Andy
.
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