M16C Datasheet, PDF (183/262 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Preliminary Specifications REV.B
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M16C / 6N Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Programmable I/O Port
Programmable I/O Ports
There are 87 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. P71 and
P91 are Nch open drain ports and have no built-in pull-up resistance. P85 is an input-only port and has no built-
in pull-up resistance.
Figures 19-1 and 19-3 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 (other than the D-A
converter), they function as outputs regardless of the contents of the direction registers. See the descrip-
tions of the respective functions for how to set up the built-in peripheral devices.
(1) Direction registers
Figure 19-4 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 P85.
(2) Port registers
Figure 19-5 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 19-6 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, P0 to P5 operate as the bus and the
pull-up control register setting is invalid.
(4) Port control register
Figure 19-7 shows the port control register.
The bit 0 of port control register is used to read port P1 as follows:
0 : When port P1 is input port, port input level is read.
When port P1 is output port , the contents of port P1 register is read.
1 : The contents of port P1 register is read though port P1 is input/output port.
This register is valid in the following:
• External bus width is 8 bits in microprocessor mode or memory expansion mode.
• Port P1 can be used as a port in multiplexed bus for the entire space.
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