lrdazmmlk, you started a new topic with the same question. It might be merged with this one.
Can you tell us:
1 ) Do you want to use a timer for 125 kHz output. That is possible.
2 ) Do you want to create an interrupt of 125 kHz, that will not be reliable. It might work for a short time, but I don't know why that can be helpful for something.
3 ) How will this help with reading a signal of 125 kHz after a few µs of the rising edge ?