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Generating 100us timer base & cnt (STM32F205)

Question asked by takniki.vindhyachal on Nov 4, 2014
Latest reply on Nov 4, 2014 by Clive One
1. I have STM32F205 running at 120Mhz with external 16Mhz crystal.
Prefetch , Data & Instruction buffer on. timer is clocked by 60Mhz

2. task is to toggle 10 pins with a base count of 100us.
i.e User will enter number in multiple of 100us & I have to toggle the pins.

3. I have timer base of 100us &  accordingly I am toggled the pins. In interrupt only 10 variables are incremented. So ISR is very small.

4. System works fine initially but on long run (1 hour or so), I saw some latency keep on adding. 

5. This probably due to small time base i.e 100us. It adds jitter & theoretically Cortex-M3 core should always be able to service an interrupt request within 15 cycles 
. Is it due to these cycles which accumulate over period of time & generate error.

6. Any possible solution/advise/technical point