Programmable I/O Ports; Direction Registers; Port Registers; Pull-Up Control Registers - Renesas M16C Series User Manual

M30240 Group

1.2.26 Programmable I/O Ports

There are 63 programmable I/O ports: P0 to P3, P6 to P8 (excluding P8
set independently for input or output using the direction register. A pull-up resistance for each block of
4 ports can be set. P8
Figure 1.106, Figure 1.107 and Figure 1.108 show the programmable I/O ports.
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, they function as
outputs regardless of the contents of the direction registers. Unused I/O pins can be terminated as
shown in Figure 1.113 and Table 1.36 .

1.2.26.1 Direction registers

Figure 1.109 shows the direction registers.
These registers are used to choose the direction of the programmable I/O ports. Each bit in these reg-
isters corresponds one for one to each I/O pin.
Note: There is no direction register bit for P8

1.2.26.2 Port registers

Figure 1.110 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.

1.2.26.3 Pull-up control registers

Figure 1.111 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.

1.2.26.4 High drive capacity registers

Figure 1.112 shows the Port 2 and PWM drive capacity register. Port 2 can be configured to drive an
LED by increasing the drive strength of the corresponding bit's N-channel transistor. Each Timer out-
put (TA0 toTA4
OUT
the corresponding bits.
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is an input-only port and has no built-in pull-up resistance.
5
) can be configured for high-drive capability by increasing the drive strength of
OUT
.
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Programmable I/O Ports
), and P10. Each port can be
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