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PIC input

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hkit711

New Member
Hello all, I', wondering wich voltage is concidered as "0" low in PIC inputs.
"0" volt to...???

Thanks
 

eblc1388

Active Member
mneary said:
It depends on the PIC family, and what voltage you're using for Vcc.

To make matter worse, all of the above by mneary and which pin on the PIC is being used for input.

Some pins on the PIC have schmitt trigger characteristic and require higher input level than remaining pins.
 

ericgibbs

Well-Known Member
Most Helpful Member
hkit711 said:
Hello all, I', wondering wich voltage is concidered as "0" low in PIC inputs.
"0" volt to...???

Thanks

As already stated, get the datasheet for your PIC. from: www.microchip.com

Search the datasheet.pdf for 'AC and DC characteristics' they are near the end of the datasheet, they tell you all you need to know.:)
 

Sceadwian

Banned
eblc is right though, it depends on the pin. Pin's used for various onboard peripherals can have different driving circuitry. So you need to consult the PDF's peripheral section when it's being used as a general IO pin.
 

szabi

New Member
Does anybody know that a pin configured as digital input consumes less power if it's pulled up or down?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
szabi said:
Does anybody know that a pin configured as digital input consumes less power if it's pulled up or down?

I don't think it makes much, or any, difference? - but it would be childs play to measure it and find out!. Bear in mind the input pins are VERY high impedance.

The conventional method is to use pull-ups, and MicroChip even provide switchable internal pull-ups on PortB.
 

Gordz

New Member
No digital inputs should be left 'floating' as this creates problems with noise and current draw. As Nigel said, the PIC's have an option for weak pullup to solve this issue.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Gordz said:
No digital inputs should be left 'floating' as this creates problems with noise and current draw.

This is only a concern with CMOS logic chips, it doesn't appear to affect PIC's at all? - there was a big thread, and LOT'S of testing done, years ago on the PICList.

If you do have an unfounded fear of such a problem?, simply leave the pins open, but set them to be outputs - and again, setting them as outputs makes no difference to the current consumption (same old thread on the PICList).
 

Gordz

New Member
Perhaps it's just an old habit then, it used to be good practice to 'keep digital inputs tidy' and NOT just on CMOS. By the way, TTL gate inputs tend to 'float' high and often data sheets stipulate 'tying unused inputs' high or low.
 
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