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Pull up and pull Down Resistors in micro controllers

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Bjtpower

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Hi All

I am looking to gain knowledge on Micro controller Hardware Design.

For that, i need to know about Pull up and Pull down Concepts.

I have controller of Pic Controller over where i am using 50 Pins.

now the rest pin Floating.

i want to fix them with the Pull Up or Pull Down Resistor.

I dont know what is the Purpose and how we can do the same that Particular pin should be PulLED UP OR Pulled Down..??

Looking for gaining some Knowledge..

Thanks
Marx
 

microcontroller reset pin is always high but when u pressed reset button it goes low this is what makes microcontroller reset. Just connect given config to reset button. Untitled.png
 

For that, i need to know about Pull up and Pull down Concepts.
i want to fix them with the Pull Up or Pull Down Resistor.
I dont know what is the Purpose and how we can do the same that Particular pin should be PulLED UP OR Pulled Down..??
A pullup or pulldown is used to ensure there is a valid logic level on an input pin or to "park" an output pin at either high or low logic levels.

If you don't us a pullup/pulldown on an input the input floats and it may sit at a value that results in both transistors in the input partially conducting wasting power and heating the part. It may also get interpreted by the input as a high (or a low) that may not be what you want the pin to be (e.g. like the reset being at the incorrect level to allow the part to work).
 
You have to go pin by pin (or pin-class) and determine
what the "do nothing" state is; that's generally where
the passive pull-to should be. If reset is active low, you
want not-reset (high). Same idea for interrupt pins if you
don't want constant interruption. Data, like parallel ports,
can probably go either way and just let the software
folks know what to expect.

Often datasheets have application or test method figures
which yield clues about what's considered normal.
 

What is hardware inside a Port.?
Dedicated input Pin..??
GPIO..?
Dedicated output Pin..??


If i know the Inside Knowledge then i will get better Idea.

Weblink/Articles appreciated..!!

Thanks
Marx
 

The hardware inside a pin might be specified in the devices data sheet which will also tell you the "power on reset" condition for each pin and internal register (which will answer the default input/output question).
You have not told us which microcontroller you are looking at so it is very hard to provide links, but all manufacturers will publish the data sheet and probably all sorts of additional documentation about their devices.
Susan
 

What is hardware inside a Port.?
Dedicated input Pin..??
GPIO..?
Dedicated output Pin..??


If i know the Inside Knowledge then i will get better Idea.

Weblink/Articles appreciated..!!

Thanks
Marx

Why do you need (being a programmer) to know the transistor circuit inside the device (the hardware inside a port)? You can see an example of the type of circuit used for an input and output of a gate based on the CMOS schematic in this TI AND gate: https://www.ti.com/lit/ds/symlink/cd4073b.pdf. Look at page 3-191.

I took a quick look with a bunch of different search terms an couldn't find what any first year electronics engineering course on digital design would have shown basically a transistor circuit based on either CMOS or bipolar. What they likely won't show in any of those texts would be the input protection circuits they add to protect the input from ESD, over/under shoot, and other "bad" things.
 

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