I?m looking for just the right counter/timer module to perform a veryspecific task. I have a quadrature encoder turned by an enginecrankshaft. The encoder has the usual A-phase, B-phase and Indexoutputs. With respect to the encoder?s Index pulse, the count ofA-phase pulses defines various angles of the crankshaft. I need togenerate signals where each transition is individually programmed tooccur at a specific crankshaft angle. Two consecutive outputtransitions will always be far enough apart so that firmware canintervene to set up the next transition. This seems to call for theoutput 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 andan external counter reset function? The output compares in theMicrochip family don?t seem to have the automatic reset function. Iam open to both counter/timers as part of microcontrollers orindependent devices such as the 9513 chip. (But I have examined all 24operating modes of the 9513, and none of them will do the job.) Theencoder pulses at their fastest are 2 usec. apart.-Robert Scott Ypsilanti, Michigan

Can you just do it with a high-priority interrupt triggered off theindex pulse? 2usec is a lot of time-- you may be able to skip some ofthe context save/restore overhead if you just want to get in there andreset the counter, clear the interrupt flag and get back to whateverelse is going on. Best regards, Spehro Pefhany-- "it's the network..." "The Journey is the reward" Info for manufacturers: software/hardware/analog Info for designers:

The Perfect Counter/Timer Circuit?

Jul 11, 2005 22 Replies

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Chris Carlen 20 years ago

Oh, bummer!

I used the flash version of that chip

Good day!

_____________________ Christopher R. Carlen crobc@bogus-remove-me.sbcglobal.net SuSE 9.1 Linux 2.6.5

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Hans Odeberg 20 years ago

Robert Scott skrev:

You could try Renesas' H8S series. The H8S has a six-channel TPU. One of the timer modes pairs two timer channels to form a quadrature encoder. Four registers may be used for either capture or compare. The timer can be set up to reset automatically when an input capture occurs; so reserving one register for that, you still have three compare registers left.

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CBFalconer 20 years ago

Couldn't this be built out of the appropriate GAL/PAL chips? I don't know how many counter bits you want, but I suspect you could create a couple (or more) counters per chip. Then there would be no sourcing problem.

Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net) Available for consulting/temporary embedded and systems. USE worldnet address!

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