Direction Register - Renesas 7700 FAMILY User Manual

3.1.1 Direction register

This register determines the input/output direction of the programmable I/O port. Each bit of this register
corresponds one for one to each pin of the microcomputer.
Figure 3.1.2 shows the structure of port Pi (i = 0 to 8) direction register.
b7 b6 b5 b4 b3 b2
Fig. 3.1.2 Structure of port Pi (i = 0 to 8) direction register
b1 b0
Port Pi direction register (i = 0 to 8)
(Addresses 4 , 5
16 16
Bit
0 Port Pi
0
1 Port Pi
1
2
Port Pi
2
3
Port Pi
3
4
Port Pi
4
5
Port Pi
5
6 Port Pi
6
7
Port Pi
7
Note: Bits 7 to 4 of the port P3 direction register cannot be written and are fixed to "0" at reading.
Bit
Corresponding
pin
7751 Group User's Manual
INPUT/OUTPUT PINS
, 8 , 9 , C , D , 10 , 11
16 16 16 16 16
Bit name
direction bit
0 : Input mode
direction bit
1 : Output mode
direction bit
direction bit
direction bit
direction bit
direction bit
direction bit
b7 b6 b5 b4
Pi Pi Pi Pi
7 6 5 4
3.1 Programmable I/O ports
, 14 )
16 16
Functions
(Functions as an input port)
(Functions as an output port)
b3 b2 b1 b0
Pi Pi Pi Pi
3 2 1 0
RW
At reset
0
RW
0
RW
0
RW
RW
0
RW
0
RW
0
RW
0
RW
0
3–3