I am trying to do some timing analysis for xilkernal, but the results didn't make sense to me. I am using an external pin to generate interrupt and the external pin is connected to an xps_intr whose Irq then is connected to the interrupt of MicroBlaze. I am using Spartan 3a Starter kit and clock is 62.5MHz.
1. The first test is to measure the timing from external pin raising an interrupt to ISR start, the time I got is 50us.
2, The secon test is to measure the ISR itself, the ISR code is like