A: The value depends on the system you use, the following result reference value is based on the state which the other application isn't run.
CPU: PentiumII333MHz Condition: The average measure value of system time to 1000 repeats of the callback in application that can occur next interrupt. Result: 10ms
Notice: The times of interrupt can be correctly notified even if the interrupts occur in a period less than 10ms.
In practice, the correct times were retrieved in the test of getting the 1000 pulses in the period of 100us for TTL Level boards.
Several times of 1000 times are failed to get in the period of 50us.