Programmable Ports
177
Specifications in this manual are tentative and subject to change
Rev. E
MITSUBISHI MICROCOMPUTERS
M30245 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Programmable I/O ports
There are 83 programmable I/O ports: P0 to P10 (excluding P85). Each port can be set independently for input or
output using the direction register. A pull-up resistance for each block of 4 ports can be set. P85 is an input-only
port and has no built-in pull-up resistance.
Figure 1.130 to Figure 1.132 show the programmable I/O ports. Figure 1.133 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, they function as outputs regardless of
the contents of the direction registers. See the descriptions of the respective functions for how to set up the built-
in peripheral devices.
High drive capacity register
Figure 1.134 shows the Port P7 drive capacity register. Port P7 can be configured to drive an LED by
increasing the drive strength of the corresponding N-channel transistor bits.
Port control register
Figure 1.135 shows the port control register.
The bit 0 of port control resister is used to read Port P1:
0: When Port P1 is an input port, the port input level is read.
When Port P1 is an output port, the contents of Port P1 register are read.
1: The contents of Port P1 register are always read.
This register is valid for the external bus width which is 8 bits in microprocessor mode or memory expan-
sion mode.
Direction registers
Figure 1.136 shows the direction registers.
These registers are used to choose the direction of the programmable I/O ports. Each bit in these registers
corresponds one for one to each I/O pin.
Note: There is no direction register bit for P85.
Port registers
Figure 1.137 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.
Pull-up control registers
Figure 1.138 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.
However, in memory expansion mode and microprocessor mode, the pull-up control register of P0 to P3,
P40 to P43, and P5 is invalid.
Unused pins
Table 1.64 lists an example connection of unused pins in single chip mode. Table 1.65 lists an example of
unused pins in memory expansion mode. Figure 1.139 shows an example connection for unused pins.