View Full Version : PLL Timer
01-24-2008, 09:55 AM
I don't understand the PLL for each COG. Can a COG timer be PLL to an input pin?
01-24-2008, 02:20 PM
Pll are freq multipliers. use pll:=4 to get 20mhz pll:=16 to get 80 mhz. This allows the prop to run at max speed. I don't think you can change other cogs to run at other speeds, haven't had the need for it.
I can't think of freq changes for input. The chip will read the pulses at the speeds sent. Input is only a voltage binary high or low.
Hope this helps
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01-24-2008, 03:59 PM
@bbaker: In NCO mode - AND ONLY THERE - you can use the pin 31 to control a PLL, multiplying by 16.
This x16 can be divided again by 2,4,8,...128.
It is recommended by the data sheet to not use anything else but 4 to 8 MHz as control frequency (thus gving 128 MHz max), but the limits are wider...
The main advantage is that the signak gets "smoothed" by the PLO, as the timer can give precise pulses only at binary factors. The "jitter" is mitigated by the PLL.
I generally recommend studying the enclosed diagram. It shows ALL about the timer/counters http://forums.parallax.com/images/smilies/smile.gif
Edit: Sorry. had to change some badly remembered constants http://forums.parallax.com/images/smilies/smile.gif
Post Edited (deSilva) : 1/24/2008 9:41:27 AM GMT