Specifications

S1C62N82 TECHNICAL SOFTWARE EPSON II-29

CHAPTER 3: PERIPHERAL CIRCUITS (I/O Ports)

As shown in Figure 3.5.1, the four instruction steps above

load the data of the I/O ports into the A register.

• Loading P00–P03 output data into A register

Label Mnemonic/operand Comment

LD Y,0FCH ;Set the address of input/output

;port control register

OR MY,0001B ;Set as output port

LD Y,0F6H ;Set the address of port

LD A,MY ;A register ← P00–P03

As shown in Figure 3.5.2, the four instruction steps above

load the data of the I/O ports into the A register.

P03

P02

P01

P00

A register

P03 P02 P01 P00

Data register

P00

Data register

P01

Data register

P02

Data register

P03

A register

D3 D2 D1 D0

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

MX instead of the A register.

Fig. 3.5.2

Control of I/O port (input)

Fig. 3.5.1

Loading into the A register