piclist 2002\09\03\165554a >
Thread: Fitting pulses into a time slot
www.piclist.com/techref/microchip/time.htm?key=time
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On Tue, 3 Sep 2002, Dave Tweed wrote:

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Maybe, maybe not. 14-instructions is limited, but there are tricks! For
example, you don't have to compute every thing in the 14 cycles. It's
possible to distribute processing across many 14-cycle slots. I assume
that a minimum 16-bit arithmetic will be required. 6-cycles will be
required for the phase accumulator and addition 2 (or three) for examining
roll overs. 2 more cycles are required for looping. This leaves only
3-cycles! However, if you unroll the loop then the 2-cycle loop overhead
can occur once for every, say, 32 accumulation intervals. This give
roughly 5-cycles per accumulation interval for doing other stuff.

Here's an extreme example of only 1-cycle available per iteration:
www.piclist.com/techref/microchip/pulsewidth-sd.htm
(it's pulse width measurement and not a pulse generator, but the same
conceptual programming approach is applicable.)

Scott

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