Hello
Could you tell me which is the lowest power solution in following cases?
1.set as output direction (High or Low?)
2.set as input direction with internal pullup/pulldown(pullup or pulldown?)
3.set as input direction with external pullup/pulldown（pullup or pulldown?)
Regards,
U-SK
Hi,
the reason for the termination of unused GPIOs is the otherwise potentially occurring current due to the so-called "floating nodes". Please see here below a typical cross current through the complementary CMOS stages in case of an MSP430F1121A.
The current, which can be measured at the device's supply connections, is not flowing into or out of the affected GPIO, but it's flowing across the complementary stages of the input, as the transistor stage is not completely shut off, when exposed to the critical voltage levels.
Now coming to your question. Due to the above explanations, anything, that is suitable to prevent the application of critical voltages to such a complementary stage, without causing additional currents, will prevent the floating node behavior. Thus there is also no difference in current consumption between all the three options you mentioned, as long as you don't need to do this dynamically and repeatedly. Means, as long as it is only about permanent termination of not connected GPIOs, it is rather about the costs for additional components, when using external resistors or other circuitry, to terminate the input signal.
Best regards
Peter
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