POWER-DOWN KS57C2308/P2308/C2316/P2316
8-6
PORT PIN CONFIGURATION FOR POWER-DOWN
The following method describes how to configure I/O port pins to reduce power consumption during power-down
modes (stop, idle):
Condition 1: If the microcontroller is not configured to an external device:
1. Connect unused port pins according to the information in Table 8-2.
2.Disable pull-up resistors for input pins configured to VDD or VSS levels in order to check the current input
option. Reason: If the input level of a port pin is set to VSS when a pull-up resistor is enabled, it will draw an
unnecessarily large current.
Condition 2: If the microcontroller is configured to an external device and the external device's VDD source
is turned off in power-down mode.
1. Connect unused port pins according to the information in Table 8-2.
2.Disable pull-up resistors for input pins configured to VDD or VSS levels in order to check the current input
option. Reason: If the input level of a port pin is set to VSS when a pull-up resistor is enabled, it will draw an
unnecessarily large current.
3.Disable the pull-up resistors of input pins connected to the external device by making the necessary
modifications to the PUMOD register.
4.Configure the output pins that are connected to the external device to low level. Reason: When the external
device's VDD source is turned off, and if the microcontroller's output pins are set to high level, VDD – 0.7 V is
supplied to the VDD of the external device through its input pin. This causes the device to operate at the level
VDD – 0.7 V. In this case, total current consumption would not be reduced.
5.Determine the correct output pin state necessary to block current pass in according with the external
transistors (PNP, NPN).