Comparison of I/O port chips and memory chips in 8085

In this section we will see the basic comparisons between I/O port chips and the memory chips in 8085 microprocessor.

Information is also stored in an Input Output port chip similar to a memory chip. Information of 1 byte are stored in an Input Output port chip on the other hand information of few bytes are stored in the Input Output port chips. An example to be cited as only 1 byte of information is stored in Intel 8212 I/O port chip, but 3 bytes of information are stored in Intel 8255 chip. Moreover, a large number of memory locations like 1K, 4K, 8K etc. are contained in the memory chips. We select memory chip location by the address pins A_n-0.

Secondly, for communicating there are eight lines by means of which an Input Output port chip communicates with the microprocessor. An I/O port acts as a buffer between the Input Output device and the microprocessor. But, there are only eight lines which a memory chip for the communication process with the microprocessor.

Thirdly there are many programmable Input Output port chips. By this process the user decides the way how I/O port works in the system. Intel 8255 is an example for a programmable Input Output port chip. Here the user programs for both the input and output port. Also, the user programs a port for working in several modes like basic Input Output, handshake Input Output, etc. There are also non programmable Input Output port chips. Example is Intel 8212. Here the programmable Input Output ports are much popular than non-programmable ports. Here the memory chips are only chips for storing information, and they are not programmable.