ISR entry/exit speed of the SAM3X8E


does anyone know how many clock cycles the sam3x8e needs to enter and exit an ISR?

That depends on your code. The fastest would be to enter set a flag and exit. Also it also depends on what instruction is being executed at the time of interrupt. Remember it also pushes data on the stack when entering and pops data off when leaving. It also depends if it is nested or the first interrupt and if it gets interrupted or not. The data sheet will give you a lot more details then I can here.

An interruption will need ~10 clock cyles to enter, and ~10 more to exit. Add to these 20 clock cycles your code inside the interruption.