Dave VanHorn wrote:
.........
>>With an xtal frequency of 10Mhz, your choices of PWM frequencys that will
>>still give you maximum 10-bit duty cycle resolution are:
>>
>>2,500,000 / 256 = 9,765.625 hz
>>2,500,000 / (256 * 4) = 2,441.40625 hz
>>2,500,000 / (256 * 16) = 610.3515625 hz
>
>The chip giveth, and the chip taketh away..
>I definitely need to switch better than 9.7k, looks like 7 or even 6 bits
>is about the best I'll be seeing.
>
>Ok, well at least I understand the machine now. Thanks :)
>(Maybe the mfgrs should let us re-write their manuals for them!)
>

With 20 Mhz xtal, you can get 10-bit PWM at 19.53 Khz, and 8-bit at
78.12 Khz.

Another thing that the 2nd gen PIC PWM system gives you is a really
fine, digitally-controllable precision pulse generator. With a 20 Mhz
xtal, you can get short 50 nsec pulses at up to 5 Mhz rep-rate.
Because you can set 256 different values into PR2, you can get 256
adjacent rep-rates, in addition to 1024 pulsewidths. By using the
/4 and /16 prescalers, you can greatly increase the overall
frequency range. I wrote an appnote to this effect a while back:

"AN-ECD06 - Precision 50-nsec Pulse Generation Using a PIC16C63"

http://www.sni.net/~oricom/appnotes.htm

best regards,
- Dan Michaels
Oricom Technologies
===================

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