The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

PROGRAMMING THE 8255Mode Selection

of 8255(cont’)

D0

D1

D2

D3

D4

D5

D6

D7 1 = I/O MODE0 = BSR Mode

Mode Selection00 = MODE 001 = MODE 11x = Mode 2

Port A1 = Input0 = Output

Port C(Upper Pc7 – PC4)1 = Input0 = Output

Mode Selection0 = MODE 01 = MODE 1

Port B1 = Input0 = Output

Port C(LowerPC3 – PC0)1 = Input0 = Output

8255 Control Word Format (I/O Mode)

Group A

Group B