Introduction - If you have any usage issues, please Google them yourself
INT0 interrupt service routine and pulse width measurement
Produced by key/INT0 valid signal, the output signal indicating the P3.4 pin and measure the pulse width of the key high-level operations on the/INT0 pin is generated. Note: the actual operation, the pulse width of the test is likely to exceed the range of 16-bit timer counter. Operation, considered as a status indicator buzzer or tips.