PIC16F18857 external timer_0 setup help needed

[edbfmi1]

gaugeguy:

The data sheet shows it using the pins for the external resonator that my previous reply lists. Why would the data sheet show this if you can't use it?

[temtronic]

As Mr. T points out the SOSC is designed for 32KHz operation, so no you can't use 4MHz rez. It's in the datasheet 'SOSC(32KHz) ' on front pages...in the 'pin use' charts sosc(32 KHz)..... NOT listed in the 'clock section' at all,though the diagram does show it.. no specs in the back for SOSC either that I could see.

The easy solution is to just use a real 4MHz xtal as the 'primary' clock. Should be do-able ?

[Ttelmah]

If you need to run the timer off 4MHz, you can do this _by using an external
clock generator_.
However the whole 'point' of the oscillator available on this is to do things
like handle an RTC using low power. Hence this oscillator is built to use the
least possible power (so you can run it when the main chip is sleeping),
and as such does not have the power to drive a resonator above 32KHz.
As I pointed out the data sheet says that this resonator is designed and
specified to only run very slightly each side of 32768Hz.
It is in the datasheet.
Table 38-17
Parameter 48 Ft1
Secondary Oscillator Input Frequency Range
(oscillator enabled by setting bit T1OSCEN)
32.4 to 33.1 KHz........