How to Switch Off Pic?

arrow · Joined: 17 May 2005 Posts: 213

Hi

I would like to switch off the pic (not put it into sleep mode) in the middle of the code (in an if block).

Can someone please tell me how to do this?
Thank you in advance.
a.

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

You can cut off the pic's own power if you put a PNP transistor (or better,. a FET) in the power supply line, with another one, a NPN pulling its base low when active (applied high on its base). This circuit must be started manually, will be runnnig as long as the PIC keeps the output high. The PIC can commit suicide by pulling low the port (switch off its own power, one-time after manual restart of course)

arrow · Joined: 17 May 2005 Posts: 213

Hi Libor

Thank you for your reply.

I was wondering if there is a software way to switch off the PIC?

Regards
a.

Humberto · Posted: Thu Dec 27, 2007 7:56 am

Do not forget that if you switch off a PIC you also lose its control.
There are a lot of MCU with nanoWatt low sleep features, that properly configured,
drain only a few microamps.

Humberto

arrow · Joined: 17 May 2005 Posts: 213

Hi Humberto

Thank you for your reply.
I really need to switch off the PIC. I am contemplating to use a goto statement which will send the program to the end. Is there a better way of switching off?

Thank you
a.

Heath · Joined: 21 Dec 2007 Posts: 41

Please give some more information. What do you mean by 'switching off'?

What is the objective? What are you trying to accomplish by 'switching off".

arrow · Joined: 17 May 2005 Posts: 213

Hi

What happens if I put the PIC into sleep mode and then switch off the power to the PIC?

Will this damage the PIC?
When I reapply the power will it be in sleep mode?

Thank you
a.

dyeatman · Joined: 06 Sep 2003 Posts: 1923 Location: Norman, OK

The answer to your first question is the PIC simply stops running and goes to sleep.

The answer to your second question is no, it will not damage the PIC.

When the PIC is powered on it will always come up in normal run mode (third question) unless you put it back to sleep with the SLEEP() command (which is the answer to your earlier question).

See page 229 of the latest manual for info for what happens in sleep mode with the SLEEP() command.

As was said earlier, to completely remove power from the PIC will require some external circuitry.

And finally, READ the DATA SHEET and the CCS Manual, they will answer many (if not most) of the questions that you ask.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

With most PICs if you use an external clock you can just stop the clock. When you restart the clock the PIC will continue where it left off, but you must keep voltage applied for the PIC to keep its status. The power draw with no clock is minuscule. This will not work with a PIC using a PLL clock.

If you put a PIC in sleep mode, kill power, and re-apply power it will go through a normal power-on restart and start running the program from the beginning.
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arrow · Joined: 17 May 2005 Posts: 213

Hi

Thank you all for your replies and help.
I appreciate it!

All the best
a