Intel 8255 i8255

The 8255 gives a CPU or digital system access to programmable parallel I/O.[6] The 8255 has 24 input/output pins.[7] These are divided into three 8-bit ports (A, B, C).[8] Port A and port B can be used as 8-bit input/output ports. Port C can be used as an 8-bit input/output port or as two 4-bit input/output ports or to produce handshake signals for ports A and B.

The three ports are further grouped as follows:

Group A consisting of port A and upper part of port C.
Group B consisting of port B and lower part of port C.