3 month countdown alarm (miniature circuit)

JohnInTX

Joined Jun 26, 2012
4,560
Post #2.
ak
Indeed! and I should have quoted that. That's what got me going on thinking a lower power PIC. I'm right on board with using the uC approach over other ICs. The 10F200, though, besides being a nasty baseline PIC, has a fixed 4MHz clock so it's going to pull more than the XLP stuff with programmable clocks...
 
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djsfantasi

Joined Apr 11, 2010
7,843
From microchip, their recommendations on what to do with unused pins for low power consumption :

http://www.microchip.com/forums/m/tm.aspx?m=458653&p=1

"
what uChip suggested is waht every experienced hardware (digital + uCs) would suggest. So would I.


The point is: a pin needs termination only if it is an input. If it is an output it does not. The input buffer is internally connected to the output push/pull or OD (in this case output LATx must be 0) and that push-pull actually terminates the input. Nothing esle is necessary.

In case of OD (open drain) output: it must be programmed to low level so the drain would short to the source (ground = common). If the OD output is programmed to a high level the the input buffer is floating - not terminated.

If the port is used for an alternative function (UART Rx/Tx, SPI etc.) that alternative function takes control and initializes the port. BUT it is always a good practice to properly initialize TRIS/LAT or PORT registers.

I have seen cheap (low or really bad quality) uCs like some from NEC, Toshiba and others that require pulling up OUTPUTS :). Yes, outputs. But we are not talking about mutant quality uC :)

So any unused pin = output, low level as a general rule. Of course there may be some special cases so think about and consider any details of the particular design.

For an instance immediatelly after power up all ports are inputs. If your design has something very special and sensitive contrlled by an output of the uC it may need a pull-up/down on an output just for those us/ms after power up."
 

JohnInTX

Joined Jun 26, 2012
4,560
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