PIC Timer 0 as timer -- which clock speed is best?
Posted: Fri Jul 24, 2015 3:13 pm
When using Timer 0 as a timer to count elapsed seconds as a 'background' process, I guess it's sensible to run the clock at a rate that minimizes the interrupts per second and thereby minimizes interference with the 'foreground' process, but which clock speed is best?
Given that the target chip (PIC16F88) has byte-only arithmetic, I will need to count timer overflows in multiples of 255. Accuracy is not absolutely critical in this application, nonetheless I would like the elapsed time to be as accurate as possible given the available clock and prescalar options available.
Here are the Interrupts Per Second rates for the PC16F88 using either 4MHz or 8Mh clock speed:
Environment
Chip: PIC16F88 (byte only, no float data type)
Timer: Timer 0
Mode: INTRC as Port I/O
Given that the target chip (PIC16F88) has byte-only arithmetic, I will need to count timer overflows in multiples of 255. Accuracy is not absolutely critical in this application, nonetheless I would like the elapsed time to be as accurate as possible given the available clock and prescalar options available.
Here are the Interrupts Per Second rates for the PC16F88 using either 4MHz or 8Mh clock speed:
Code: Select all
Clock-> 4Mz 8Mz
Prescalar
1:1 3906.250 7812.500
1:2 953.125 3906.250
1:4 976.563 1953.125
1:8 488.281 976.563
1:16 244.141 488.281
1:32 122.070 244.141
1:64 61.035 122.070
1:128 30.518 61.035
1:256 15.259 30.518
Chip: PIC16F88 (byte only, no float data type)
Timer: Timer 0
Mode: INTRC as Port I/O