Hi, I have a general doubt on keeping the unused micro pin open. what i generally suspect is whether keepin the unused micro pins will lead do EMC/EMI problem in the board or not? if so can anybody explain the scenario. Also What should be the state of these unused pins like configuring as input/output, pulling up/down? Please suggest me to proceed.
Regards, Nag.
Depends.
What does the data sheet say about the chip you have not told anyone about.
What is the status of this pin at RESET ?
Input/Output/Tristate/pullups/pulldowns/Open Collector/Totom Pole.
Give me a clue and I'll give you an answer.
donald
How much are you paying ?
Graham
Tie unused inputs to Vss; a 10K is a good place to start.
Unused outputs (e.g., to an infrequenty used test port) should have series resistors sufficient to limit their current in the event that the outputs (one or all) are accidently shorted to Vss or ground.
Spare pins can be productive as extra outputs for status/debug/test.
A spare bidirectional bit on an I/O port could be tied to Vss via a
10K and still be used (with care) as either an input or an output.-- Rich Webb Norfolk, VA
Hi Donald, The reset configutation of my micro is all the ports are configured as input port. If it is input port there are two configuration like TTL logic and special threshold logic. Default is TTL logic. If we configure it as outport through the internal configuration register there are again three output modes. Strong, Medium and Weak driver configuration. Each configuration is push/pull transistor internally. Can you suggest me what shoud be the default configuration for the unused port pins?
Nag.
I can ensure that the unused port pin will not have contact with either Vss or Ground. In that case still do i need to connect this pin to Vss through 10K resistor. If i don't do that whether high current consumption problem or EMC/EMI problem will happen to the Micro?
Regards, Nag.
Configure it as an output and set it either high or low if you're worried.
Graham
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