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10.1.4
Port States in Low Power Modes
The D
0 to D4 pins and the R0, R3, and R4 port pins have shared functions as input or output pins
for built-in peripheral modules. In standby mode, since the CPU stops, the pins selected as output
ports maintain their immediately prior output values. Also, pins selected for use by built-in
peripheral modules that operate in standby mode continue to operate. (Output pins used by
modules that stop in standby mode maintain their immediately prior output values.) See section 5,
“Low Power Modes”, for details on which built-in peripheral modules can operate in each mode.
Table 10-5 lists the port states in the low power modes.
Table 10-5 Port States in Low Power Modes
Low Power Mode
Port States
Standby mode
Pins maintain their values immediately prior to entering standby mode.
Stop mode
Built-in peripheral function selections are cleared, and the port and
peripheral function I/O pins go to the high impedance state.
10.1.5
Handling Unused Pins
I/O pins that are unused in user systems must be tied to a fixed potential, since floating I/O pins
can cause noise that can interfere with LSI operation.
The built-in pull-up MOS transistors can be used to pull up unused pins to V
CC. Alternatively,
unused pins can be pulled up to V
CC with external resistors of about 100 k.
Application programs should maintain the PDR, DCD and DCR contents for unused pins at their
reset state values. Also note that unused pins must not be selected for use as peripheral function
I/O pins.