Quote Originally Posted by financecatalyst View Post
How do I know which PICs need this DEFINE statement and which don't?
The same way you know about all the other things the chip does ... the Datasheet. (Oscillator section)
Only the really OLD chips need OSCCAL calibration.

I am trying to serout with 12F635 & serin at 16F676. It is still giving problems, does 635 also needs some kind of calibration? Thanks
No, the 635 doesn't need an OSCCAL.
It has a precision multi-speed internal oscillator, and you can select the speed with OSCCON. But it defaults to 4Mhz.
It's factory calibrated, and the calibration can not be erased.

The 635 has a comparator that needs to be turned off though.
CMCON0 = 7
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