Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

PROGRAMMING THE 8255Mode Selection

of 8255

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While ports A, B and C are used to input or output data, the control register must be programmed to select operation mode of three ports

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The ports of the 8255 can be programmed in any of the following modes:1.Mode 0, simple I/O ƒ

Any of the ports A, B, CL, and CU can be programmed as input out outputƒAll bits are out or all are inƒThere is no signal-bit control as in P0-P3 of 8051