Re: PIC MCU timer1\timer0 maximum external clocking frequen
I see this is an old topic - but just for the record, I believe, on the 16F series, the mimimum period you can measure with the imer0 prescaler set to 256 is 40nS - makes the maximum freq. directly into input of PIC -> 25Mhz.
I am not sure if this is applicable for 18F series and higher though - maybe other can write their experience.
Sir,
I want to know how did you calculate the minimum period which can be measured with timer0 prescaler?
As i am using 16f887 timer0 to measure the time period of 10ms.
for that purpose i have omron h3cr-f8 timer but with this timer i can get the pulse minimum of 20ms.
i want to count the pulse occured in every 1/3 second using above mentioned ( 0.2 to 1.2second time range) i am getting 1:1 count with prescaler rttc_div_8. ( TRIAL AND ERROR). I have check the count using wdt prescaler but there is no 1:1 result.
may be these are basic questions but i need help .
a)I want to know how can we calculate prescaler for given pulse width?
b)As mentioned in the datasheet that
>>>"for 1:1 prescaler should be assigned to watchdog" .
>>>but there is also mentioned that "When Timer0 is in Counter mode, the synchronization
of the T0CKI input and the Timer0 register is accomplished
by sampling the prescaler output on the Q2 and
Q4 cycles of the internal phase clocks. Therefore, the
high and low periods of the external clock source must
meet the timing requirements."
I am not getting what these two statements say
for 10 ms pulsewidth what prescaler should be used ( INTERNAL OSCILLATOR 2MHZ)?
thanks in advance.