funlw65 wrote:
> Hmm, guys you forgot about this:
>
> assembler
> -- ========================
> bsf _status, _rp0 -- bank 1
> -- ========================
> call 0x3ff -- get the factory calibrated OSC value
> movwf osccal -- for accurate timing
> -- ==================
> bcf _status, _rp0 -- bank 0
> -- ==================
> end assembler
You are right that OSCCAL should be loaded with the calibrated value in
that high-memory location. And not only for the 2 PICs you mention, but
also for a number of others. I have a note in my todo list: 10Fs,
12F508,509,510,519,629,675 and 16F505,506,630,676, maybe more.
I think a simple 'asm movwf OSCCAL' as very first instruction will be
enough, because with a reset the program counter is set to the last
memory location (e.g. DS41239D 4.7.1 and 9.2.2).
Changing OSCCAL is fine tuning, omitting OSC calibration will not be the
cause that a led doesn't blink at all, only the blink frequency may be a
bit different.
When an accurate frequency is a required an external oscillator is the
way to go.
We have discussed the OSCCAL issue in the begin-period of the Jallib
group and decided then to spend out time on more urgent things.
> Should be included in device file for 12F629 and 12F675.
And in some others, if in the device files at all. It requires
co-operation with the compiler, because the compiler decides where code
is store in memory. Maybe it should be a pragma.
> Also, you
> must pay attention at burning time, to not override that location of
> flash memory....
True, use a proper programmer!
Regards, Rob.
--
Rob Hamerling, Vianen, NL (http://www.robh.nl/)
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