Programmable I/O Port
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Preliminary Specifications REV.E
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M30220 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
142
Programmable I/O Ports
There are 104 programmable I/O ports: P0 to P13 (excluding P7
7
). 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. P7
7
is
an input-only port and has no built-in pull-up resistance.
Figures 1.19.1 to 1.19.4 show the programmable I/O ports. Figure 1.19.5 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 1.19.6 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 P7
7
.
(2) Port registers
Figure 1.19.7 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 1.19.8 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. The pull-up resistance is not connected for pins that are set for output from peripheral
functions, regardless of the setting in the pull-up control register. When pull-up is ON for ports P1 and P2,
an intermittent pull-up that pulls up the port for only a set period of time, can be performed from the key
input mode register.
(4) Key input mode register
Figure 1.19.9 shows the key input mode register.
With bits 0 and 1 of this register, it is possible to select both edges or the fall edge of the key input for P1
and P2. Also, with bit 2, it is possible to make the pull-up for a port (P1 or P2), which is set for pull-up using
the pull-up control register, automatically connect as an intermittent pull-up. And, using the significant 3
bits, the pull-up resistance can be connected to and disconnected from ports P12 and P13.
(5) Real-time port control register
Figure 1.19.10 shows the real-time port control register. The real-time port control register can be used to
set the registers of ports P0, P1, P2 and P12 for real-time port output, whereby output is synchronized
with timer overflow of timers A0, A1, A5 and A6 in the timer mode. For details, see “Real-time Port”.