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6.2 Port Block Diagram
A port consists of the following hardware.
Item
Control register
Port
Pull-up resistor
Note
Memory expansion mode registers specify input/output of Port 4.
6.2.1 Port 0
Port 0 is a 5-bit input/output port with output latch. P01 to P03 pins can be set to the input mode/output mode
bit-wise with the port mode register 0 (PM0). P00 and P04 pins are input-only ports. When P01 to P03 pins are used
as input ports, a pull-up resistor can be connected to them in 3-bit units with an on-chip pull-up resistor option register
(PUO).
Alternate functions include external interrupt request input, external count clock input to the timer and crystal
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connection for subsystem clock oscillation.
RESET input sets port 0 to input mode.
Figures 6-2 to 6-4 show block diagrams of port 0.
Caution
Because port 0 is also used 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.
RD
134
CHAPTER 6 PORT FUNCTIONS
Table 6-3. Port Block Diagram
Port mode register
Pull-up resistor option register
Memory expansion mode register
Key return mode register
Total: 53 ports (2 inputs, 51 inputs/outputs)
• Mask ROM versions
Total: 51 (software control: 47, mask option control: 4)
• µ PD78P014, 78P014Y Total: 47
Figure 6-2. P00 Block Diagram
RD
Edge detection
: Port 0 read signal
Configuration
(PMm: m = 0, 1, 2, 3, 5, 6)
(PUO)
Note
(MM)
(KRM)
P00/INTP0/TI0
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