Hi ST expert,
I am trying to use SPC5 as a multi-channel PWM controller. Normally for this kind of application, the duty cycle calculation will be done in an interrupt. For 100kHz PWM, the allowed interrupt duration is <10uS, for example 8uS max. The rest of time (10uS-8uS=2uS) should be reserved for other processes, such as communication etc.
As there is a lot calculation for multi-channel PWM, it is necessary to maximize the usage of the interrupt duration. However, I found it will take >1.2uS to enter an interrupt and take another 1uS to go back to the main routine for 48MHz clock. That means >40% of the interrupt duration will be wasted. Attached is my program used to test the interrupt duration and the captured waveform - PIT Channel 1 as the trigger source; PC9 is the output.
My question here is why SPC5 needs so many clocks to enter and left the interrupt and is there any way to reduce such unnecessary timing?