Answer:
There are two basic operational modes of 8255:
Bit Set/Reset mode (BSR mode).
Input/Output mode (I/O mode).
Features of 8255 Microprocessor:
Mode 0 : Simple Input/Output.
Mode 1 : Input/Output with handshake.
Mode 2 : Bi-directional I/O data transfer.
It has three 8-bit ports : Port A, Port B, and Port C, which are arranged in two groups of 12 pins.
The 8255 can operate in 3 I/O modes : (i) Mode 0, (ii) Mode 1, & (iii) Mode 2.