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4.2 Port Configuration
A port consists of the following hardware.
Item
Control register
Port
Pull-up resistor
4.2.1 Port 0
Port 0 is an 8-bit input/output port with output latch. P00 to P07 pins can specify the input mode/output mode in
1-bit units with the port mode register 0 (PM0). On-chip pull-up resistor can be used in 1-bit units with a pull-up resistor
option register 0 (PU0).
Alternate functions include external interrupt request input, serial interface data input/output, and clock input/
output.
RESET input sets port 0 to input mode.
Figure 4-2 shows a block diagram of port 0.
Cautions 1. Because port 0 also serves for external interrupt request input, when the port function output
mode is specified and the output level is changed, the interrupt request flag is set. Thus,
when the output mode is used, set the interrupt mask flag to 1.
2. When port 0 is used as the serial interface pins, an I/O and output latches must be set
according to the functions to be used. For an explanation of how to set these latches, refer
to the description of the format of the serial operation mode register.
CHAPTER 4 PORT FUNCTIONS
Table 4-2. Port Configuration
Configuration
Port mode register (PMm: m = 0, 2 to 6, 8, 9)
Pull-up resistor option register (PU0)
Total: 56 (5 inputs, 16 outputs, 35 inputs/outputs)
Total: 8 (software specifiable: 8)
Preliminary User's Manual U14581EJ3V0UM00
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