gbbickerton
Member
Does anyone know what the maximum count frequency is for 'settimer' is when it is used in the external counter mode. I expect it will be much greater than the count command which will be useful for a frequency counter.
settimer maximum count frequency
- Thread starter gbbickerton
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hippy
Ex-Staff (retired)
Yes, the frequency accepted will be far higher than COUNT.
I couldn't find the data in the 28X2 (18F25K22) datasheet and the 28X2-3V (18F25K20) which should be similar is a bit ambiguous ...
Tt1P - T13CKI Input Period = 60ns (min) -- which I take as 16MHz
but then
Ft1 - T13CKI Oscillator Input Frequency Range = DC to 50kHz (max)
On the 20X2 I've used the internal counter driven from 8MHz and it seemed to work so I'd have thought that would be the same on 28X2, and 16MHz wouldn't be unreasonable, with that 50kHz being a typo or my misunderstanding of what the figure actually is.
Added : I'm guessing "Oscillator" is the clue. When using an external watch crystal oscillator that's DC-50kHz, direct drive up to 16.6MHz.
I couldn't find the data in the 28X2 (18F25K22) datasheet and the 28X2-3V (18F25K20) which should be similar is a bit ambiguous ...
Tt1P - T13CKI Input Period = 60ns (min) -- which I take as 16MHz
but then
Ft1 - T13CKI Oscillator Input Frequency Range = DC to 50kHz (max)
On the 20X2 I've used the internal counter driven from 8MHz and it seemed to work so I'd have thought that would be the same on 28X2, and 16MHz wouldn't be unreasonable, with that 50kHz being a typo or my misunderstanding of what the figure actually is.
Added : I'm guessing "Oscillator" is the clue. When using an external watch crystal oscillator that's DC-50kHz, direct drive up to 16.6MHz.
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