On Mon, 2005-03-28 at 13:57 -0500, Olin Lathrop wrote:
> Herbert Graf wrote:
> > In table 21-1 (oscillator operating modes): FRC 8MHz internal RC
> > oscillator (with an odd 7.5MHz for the 16X PLL, I thought that was just
> > a typo).
> >
> > In section 21.2.5 (Fast RC Oscillator) it says 8MHz nominal.
> >
> > Table 24-5: FRC (~2MIPS)
> 
> This is probably because the oscillator frequency was changed and they
> neglected to update the various mentions to it in the main part of the
> manual, with only the real spec in the back getting updated.

Yup, which of course makes one wonder: what else did they get wrong! :(

> The reason for the change is that 8MHz is just a little too fast to use with
> the 16x PLL.  The max it can take is 7.5MHz.  So the oscillator became
> roughly "7.5MHz", except that 7.3728MHz is the next lower "baud rate"
> frequency.  For some reason I can't imagine, the high speed baud rate mode
> was dropped from the dsPICs, so having a frequency that is a multiple of
> standard baud rates is more important than it would otherwise be.  Note that
> 7.3728MHz is also the standard crystal frequency for running a dsPIC at
> "maximum" speed.

Yes, I noticed that, very frustrating, I guess MChip just didn't think
many people would use a dsPIC at standard USART rates.

I don't mind the fact they changed the FRC to that freq, but if they
would only change the documentation properly!??

> > Table 24-13: Oscillator Frequency - FRC - typical: 7.3728MHz??!??!?
> 
> Yeah, plus or minus what?  Specifying an RC oscillator to 5 digits is just
> irresponsible, even if it is a typical spec.

Hehe, I thought the same thing! TTYL
 

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

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