Re: PWM1 & PWM3 synchrounization problem!!

MSAD wrote:
Dear all,
Good day!!
I am setting COMPR1 and COMPR2 to produce two variable-duty cycle PWM
signals. although both signals are having the same period etc. (off course
with different compare values). However, unfortunetly, what I am having on
the Oscelliscope is that one signal is travelling with respect to other
one.
on the other hand, if i use the same table (compare values) for both
COMPR1 and COMPR2 then both signals will be in sync. (tied to each
other).
hence, I can't really understand what makes one of them travelling with
respect to the other since both of them are using the same timer1 and same
period ,,, etc.
any comments/ suggestions would be greatly appreciated

kindes regards
MSAD

If you're going to mention specific registers you should specify what processor you're using.

Since I have no idea what processor you're using I cannot be specific, so here's some questions you can ask yourself.

* Are they really tied to one timer? Double check that manual!
* Is the timer a period register, or is this something perverse like
the Motorola (Freescale) 68HC11 where the timer always free runs
and the compare has to be jiggered in software?
* Some more advanced PWM generators will drive the timer in a triangle
wave, so the resulting PWM will be symmetrical around the peaks of
the triangle; this will result in PWM outputs that are centered on
each other, but who's edges are not synchronous.
* If you run the compares with different values for a while then go
back, to they become synchronous again?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/
.

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