toggling problem

how to toggle 500 hz with 50 hz using timer 1 ISR

the question is a bit unclear...

to toggle at 500 Hz or 50 Hz you don't really need a timer.

I am reading this as you have an interrupt that fires 500 times a second. If you want to do something 50 times a second then increment a counter when the counter reaches 10 reset to 0 and do whatever it is you want to do at 50 Hz.

I don't know if that is what you want but the only thing that makes sense based on the info you gave.

SANDIE: how to toggle 500 hz with 50 hz using timer 1 ISR

Guess the 500hz rate, and correct it as you get timing interrupts from the ISR.