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INPUT/OUTPUT PINS

7906 Group User’s Manual Rev.2.0

5-3

5.2 Programmable I/O ports

5.2.1 Direction register

This register determines the I/O direction of programmable I/O ports. One bit of this register corresponds

to one pin of the microcomputer, and this is the one-to-one relationship.

Figure 5.2.2 shows the structure of port Pi (i = 1, 2, 5 to 7) direction register.

Fig. 5.2.2 Structure of port Pi (i = 1, 2, 5 to 7) direction register

Port Pi direction register (i = 1, 2, 5 to 7)

(Addresses 516, 816, D16, 1016, 1116)

Port Pi0 direction bit

Port Pi1 direction bit

Port Pi2 direction bit

Port Pi3 direction bit

Port Pi4 direction bit

Port Pi5 direction bit

Port Pi6 direction bit

Port Pi7 direction bit

b7 b6 b5 b4 b3 b2 b1 b0

Notes 1: Nothing is assigned for bits 0 to 4 of the port P5 direction register. These bits are undefined at reading.

2: Nothing is assigned for bits 6 and 7 of the port P6 direction register. These bits are undefined at reading.

3: Nothing is assigned for bits 5 to 7 of the port P7 direction register. These bits are undefined at reading.

4: Any of bits 0 to 5 of the port P6 direction register becomes “0” by input of a falling edge to pin P6OUTCUT/INT4. (Refer to

section “5.2.3 Pin P6OUTCUT/INT4.”)

0 : Input mode

(The port functions as an input port.)

1 : Output mode

(The port functions as an output port.)

Bit name

Bit

Function

At reset

R/W

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