Mitsubishi microcomputers
M16C / 62A Group (80-pin)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Programmable I/O Port
141
Programmable I/O Ports
The M16C/62A (80-pin version) group has 70 programmable input/output ports given below (except P85).
P0
0
-P0
7
P2
0
–P2
7
P3
0
–P3
7
P4
0
–P4
3
P5
0
–P5
7
P6
0
–P6
7
P7
0
, P7
1
, P7
6
, P7
7
P8
0
–P8
4
, P8
6
, P8
7
(P8
5
is input port)
P9
0
, P9
2
–P9
7
P10
0
–P10
7
Note: P1, P4
4
to P4
7
, P7
2
to P7
5
, P9
1
are not connected to external pins.
Figures 1.18.1 to 1.18.4 show the programmable I/O ports. Figure 1.18.5 shows the I/O pins.
Each pin functions as a programmable I/O port and as the I/O for the built-in peripheral devices.
To use the pins as the inputs for the built-in peripheral devices, set the direction register of each pin to input
mode. When the pins are used as the outputs for the built-in peripheral devices (other than the D-A con-
verter), they function as outputs regardless of the contents of the direction registers. When pins are to be
used as the outputs for the D-A converter, do not set the direction registers to output mode. See the
descriptions of the respective functions for how to set up the built-in peripheral devices.
(1) Direction registers
Figure 1.18.6 shows the direction registers.
These registers are used to choose the direction of the programmable I/O ports. Each bit in these regis-
ters corresponds one for one to each I/O pin.
Note: There is no direction register bit for P8
5
.
(2) Port registers
Figure 1.18.7 shows the port registers.
These registers are used to write and read data for input and output to and from an external device. A
port register consists of a port latch to hold output data and a circuit to read the status of a pin. Each bit
in port registers corresponds one for one to each I/O pin.
(3) Pull-up control registers
Figure 1.18.8 shows the pull-up control registers.
The pull-up control register can be set to apply a pull-up resistance to each block of 4 ports. When ports
are set to have a pull-up resistance, the pull-up resistance is connected only when the direction register is
set for input.