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CHAPTER 5 PORT FUNCTIONS
5.2 Port Configuration
A port consists of the following hardware:
Table 5-2. Port Configuration
Item
Configuration
Control register
Port mode register (PMm: m = 0, 2 to 6, 8, 9)
Pull-up resistor option register (PU0)
Port
Total: 56 lines (5 inputs, 16 outputs, 35 inputs/outputs)
Pull-up resistor
Total: 8 (software specifiable: 8)
5.2.1 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). When P00 to P07 pins are used as input ports, an on-chip pull-up
resistor can be used to them in 1-bit units with a pull-up resistor option register (PU0).
Alternate functions include external interrupt request input.
RESET input sets port 0 to input mode.
Figure 5-2 shows a block diagram of port 0.
Caution
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.
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