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Question about pull up resistor

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New Member
I'm sure this is a easy/stupid question, but I'm quite new to electronics.

I want to pull voltage from the VCC pin (pin28 connected to 5v supply) on a MCU to set a address pin (pin1) high using a 10k resistor between the pins. Now if I ground pin1 with a switch I know it will go low, but will that pull pin28 low as well (act as a pull down)? If so I'll use a switch and kill the conntection between the pin28 and pin1 when 1 goes to ground, but I'm just not sure if I need to do that since the drop across the resistor should be quite low. Thank you
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
Of course it won't pull the Vcc pin low, that's what the 10K resistor is there for.

In any case, you're NOT 'pulling current' from the Vcc pin, it's coming from the power supply, the Vcc pin is essentially an 'input' not an 'output'.


Well-Known Member
No, pin 28 VCC will not be pulled low, the 10k pullup resistor between pin28 and pin 1 prevents just that.
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