Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

PROGRAMMING THE 82558255 Features

(cont’)

‰PA0 - PA7 (8-bit port A)

¾Can be programmed as all input or output, or all bits as bidirectional input/output

‰PB0 - PB7 (8-bit port B)

¾Can be programmed as all input or output, but cannot be used as a bidirectional port

‰PC0

– PC7 (8-bit port C)

¾Can be all input or output¾Can also be split into two parts:

ƒCU (upper bits PC4 - PC7)ƒCL (lower bits PC0

• PC3)

each can be used for input or output¾Any of bits PC0 to PC7 can be programmed individually

(^8255) A
PA3PA2PA1PA0-RD-CSGNDA1A0PC7PC6PC5PC4PC0PC1PC2PC3PB0PB1PB2
PA4PA5PA6PA7-WRRESETD0D1D2D3D4D5D6D7VccPB7PB6PB5PB4PB3
(^1234567891011121314151617181920)
4039383736353433323130292827262524232221