1. IN refers to moving data from the I/O device into the MP.2. OUT refers to moving data out of the MP to the I/O device.3.4.5.Three-state buffers are used to construct the 8-bit input portExternal TTL data are connected to the inputs of the buffers.Buffer outputs connect to the data bus of MP .The MP reads the contents of the eight switches that connect to any 8-bit section of the data buswhen the select ( ?) signal becomes a logic 0.When the IN (assembly) instruction executes, contents of the switches copy to the AL register.This basic input circuit is not optional and must appear any time input data are interfaced to theMP.The basic input circuit is built into a programmable I/O devices (PIO).6.Receives data from the MP and usually must hold it for some external device.• latches or flip-flops, are often built into the I/O device
The latch stores the number output by the MP from the data bus so that the LEDs can be lit with any 8-bit binary number.