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S1C62740 TECHNICAL SOFTWARE EPSON II-29

CHAPTER 6: PERIPHERAL CIRCUITS (I/O Ports)

Loading P00–P03 output data into A register

Label Mnemonic/operand Comment

;* I/O PORT

;* LOADING P00-P03 OUTPUT DATA INTO A REGISTER

;

ZIOC EQU 0D6H ;I/O PORT CONTROL REGISTER

ZPUP EQU 0D7H ;I/O PORT PULL-UP CONTROL REGISTER

ZP0 EQU 0D8H ;I/O PORT P00-P03

;

LD Y,ZPUP ;SET PULL-UP CONTROL

;REGISTER ADDRESS

AND MY,1110B ;DISABLE P00-P03 PULL UP RESISTORS

LD Y,ZIOC ;SET I/O PORT CONTROL ADDRESS

OR MY,0001B ;SET P00-P03 AS OUTPUT PORT

LD Y,ZP0 ;SET ADDRESS OF P00-P03

LD A,MY ;LOAD DATA INTO A REGISTER

;

As shown in Figure 6.5.2, the fabove program loads the data of the

I/O ports into the A register.

P03 P02 P01 P00

Data register

P00

Data register

P01

Data register

P02

Data register

P03

A register

D3 D2 D1 D0

Fig. 6.5.2

Control of I/O port (Input)

Data can be loaded from the I/O port into the B register or MX

instead of the A register.

1 2 ... 176 177 178 179 180 181 182 183 184 185 186 ... 248 249

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Epson S1C6200A Dokumentacja Strona 181