When MCS-5 1 MCU responds to the interrupt, the internal hardware automatically clears all the interrupt marks.

Not all interrupt flags are cleared by hardware. For external interrupts, when the trigger mode is jump trigger, the interrupt flag is cleared by hardware. If the trigger mode is level trigger, it should be cleared by software. For timers, the interrupt flags of Timer0 and TimerKloc-0/are cleared by hardware, and the interrupt flag of Timer2 needs to be cleared by software. For serial interrupts, it also requires software to request 0. I hope I can help you.