The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University

HANEL

MEMORY ADDRESS DECODINGUsing 74LS138 3-8 Decoder (cont’)

74LS138 Decoder

VccGND AB C

Y0 Y2Y4Y3Y5Y6Y7

G1G2AG2B Enable

Y1

Function Table

InputsSelectEnableG1 G2C B AX HX X XL XX X XH LL L LL L HH LL H LH LL H HH LH L LH LH L HH LH LH H LH LH H H

OutputsY0 Y1 Y2 Y3 Y4 Y5 Y6 Y7H H H H H H H HH H H H H H H HL H H H H H H HH L H H H H H HH H L H H H H HH H H L H H H HH H H H L H H HH H H H H L H HH H H H H H L HH H H H H H H L

CEOE

Vpp

MEMRVcc

A0 A11

D7 D0 4K*8

D0 D7 A0 A11

Y0Y1Y2Y4Y3Y5Y6Y7

ABC G2AG2BG1

A12A13A14A15GNDVcc