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 15-5Find the base address for the 8255 in Figure 15-7.Solution:

G1 G2B G2A C B A

Address

A7 A6 A5 A4 A3 A2 A1 A01 0 0 0 1 0 0 0 88H

Figure 15-7. 8255 Decoding Using 74LS138

74LS138

A2 A0A3 A1A4 A5A6 A7

A B C

Y^2

G2AG2B G1

(^8255) CS