The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

PROGRAMMING THE 8255Address Aliases

(cont’)

Example 15-4For Figure 15-6.(a) Find the I/O port addresses assigned to ports A, B, C, and thecontrol register.(b) Find the control byte for PA = out, PB = out, PC0 – PC3 = in, andPC4 – PC7 =out(c) Write a program to get data from PB and send it to PA. In addition,data from PCL is sent out to PCU.Solution:(a)

The port addresses are as follows:

CS A1 A0

Address Port

0010 00 0 0 20H Port A0010 00 0 1 21H Port B0010 00 1 0 22H Port C0010 00 1 1 23H Control Reg

(a)

The control word is 10000011, or 83H.