The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

PROGRAMMING THE 8255Connecting 8031/51 to

(^8255) (cont’)
8051 Connection to the 8255
74LS373
AD7 AD0
8255
A1 A0 D7 D0
G D Q
A14 OC
RD WR
P3.7P3.6 P2.7 P2.0ALE P0.7 P0.0
CS A1A0 D7
WRRD PA PB PC RESD0
Notice the use of RD and WR signalsƒThis method of connecting an I/O chip to a CPU is called memory mapped I/O, since it is mapped into memory spaceƒuse memory space to access I/Oƒuse instructions such as MOVX to access 8255
8255 is connected to an 8031/51 as if it is a RAM memory