Interrupt latency is the amount is the amount of time it takes a system to respond to an interrupt.
The 4 factors influencing on embedded system response to an interrupt are:
1. The longest period of time during which that interrupt is (or all interrupts are) disabled.
2. The period of time it takes to execute any interrupt routines for interrupts that are of higher priority than the one in question.
3. How long it takes the microprocessor to stop what it is doing, do the necessary book keeping and start executing instructions within the interrupt routine.
4. How long it takes the interrupt routine to save the context and then do response.
The factor 3 is found by looking the microprocessor documentation provided by the manufacturer. It is not under software control.
The other 3 items can be found in one of the two ways:
1. We can write the code and measure how long it takes to execute.
2. We can count the instructions of various types and lookup (table) in the microprocessor documentation
How long each type of instruction takes.
Factor 2 is one of the reasons that it is generally a good idea to write short interrupt routines.