As the name implies, the latch is to latch the current state, so that the data sent by the CPU will remain locked at the output of the interface circuit for a period of time, and the state will not change until the lock is released.

Buffer, divided into input buffer and output buffer. The function of the former is to temporarily store the data sent by peripherals so that the processor can take it away; The latter is used to temporarily store data sent by the processor to peripherals.