mc9s12g128 100pin Config Unused Pin

[张华荣]

When MCU is go to Full Stop Mode,because the PORTA(some pins are configed output) can not be configed Pullup,So the ununsed pin is configed output and output 1.Whether the  power consumption is lowermost?Please give me some suggestion,Thanks.

[RadekS]

For lowest power consumption, please set unused pins as digital output or digital input with enabled internal pull-up or pull-down.

In general, you should avoid situation where digital pin will be in undefined state. Middle range voltage at digital input pin (e.g. 2.5V with 5V VCC) could cause unexpected power consumption.

This is not valid for analog pins until we enable digital input buffer. After that situation will be the same as in case of digital pins.

However we should connect unused analog pins to some defined voltage at least because immunity against noise.

More details could be found for example here:

http://www.freescale.com/files/microcontrollers/doc/app_note/AN2727.pdf

or here:

http://www.freescale.com/files/microcontrollers/doc/app_note/AN3262.pdf

Note: these application nodes was created for older MCUs (250nm technology), not all information are applicable also for S12G.

I hope it helps you.

Have a great day,
RadekS

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