How about Bresenham's Algorithm to alternate imperfect periods to
produce an average that matches any "perfect" period.
Refer to Bob Ammerman work to use Bresenham-type system for PIC MCU. He
was using the counter works in the background, either by polling or
Interrupt-Driven. So, the "SuperCycle" continues to run. The timer count
the value is stored in a 3-byte register that is decremented by the
software.
Regards,
Vlad
On 2016-03-20 14:26, Martyn Smith wrote:
Hello,
First of all quick apologies for sending an email last week without
deleting all the old information from previous postings.
I have been playing around with producing 32.768 kHz from 10 MHz using
a PIC chip.
I have a real time clock calendar chip that requires a 32.768 kHz
crystal. I want to feed it with 10 MHz signal instead, so it is
synchronised to my main 10 MHz in a frequency standard I am designing.
The method I’m using has been documented before where we have two
loops running 9632 times through a 39 instruction loop and
55904 times through a 38 instruction loop, each time toggling the
output pin.
I have done this and am getting approximately 32.768 kHz with the FM
modulation as described by previous authors.
My question is should I expect exactly 32.768000000 kHz (obviously
assuming we use the same 10 MHz to drive the divider and all test
equipment)?
The closest I can get the 32.768 kHz is within about 0.1 Hz.
Does the actual model of PIC chip influence the accuracy?
Regards
Martyn
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--
WBW,
V.P.
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