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11.1.4
Port States in Low Power Modes
The D
0 to D4 pins and the R0 and R3 to R5 port pins have shared functions as input or output pins
for built-in peripheral modules. Since the CPU stops in standby and watch modes, 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 or watch mode continue to operate. (Output
pins used by modules that stop in these modes maintain their immediately prior output values.)
See section 6, “Low Power Modes”, for details on which built-in peripheral modules can operate
in each mode.
Table 11-4 lists the port states in the low power modes.
Table 11-4 Port States in Low Power Modes
Low Power Mode
Port States
Standby mode, watch
mode
Pins maintain their values immediately prior to entering standby or watch
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.
11.1.5
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 following are examples of techniques
that can prevent noise problems.
High voltage pin:
Select “no pull-down MOS transistor (PMOS open drain)” as the mask
option and connect the pin to V
CC on the user system printed circuit board.
Standard voltage pin:
Either use the built-in pull-up MOS transistor to pull the pin up to V
CC, or
pull up the pin to V
CC externally with a pull-up resistor of about 100 k.
Application programs should maintain the PDR 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.