Hallo Manfred,

there are some more pitfalls:
I don't know how your pig sensor actually works, but keep in mind, that a signal must be produced then, and only then, when the unit falls!! If there are bounces laterly, means even after minutes or so, which can often be observed when using a mechanical switch arrangement, then your micro will be forced to exit power-down all the time, and battery capacity will heavily degrade!!

You will notice this, when scrolling though your 'time 1 to 8' memory locations: Many pigs seem to have been detected in this night...

Another point is, that the monoflop, which makes the micro exit power-down, should be triggered by a clean signal, clean in a sense that the occurence of many bounces is suppressed. Especially, when the low pulse at PORT3.2 goes high, no eroneous trigger should be present.
One methode to guarantee this, is to use a monoflop at the pig sensor too, so that pig sensor gives a HIGH pulse of a duration of MORE than 100msec, if 100msec is the pulse width of monoflop at PORT3.2 pin.
If you choose for the pig sensor monoflop a pulse width of let's say 200msec, then micro will exit power-down without any imperfections.

As Oleg already mentioned: Exiting of power-down can only work with level activated interrupt, The reason is quite easy: For an edge triggered interrupt the oscillator must run, because the change of /INT0 from high to low within two subsequent machine cycles is detected. But if the oscillator is stopped in power-down, there are no machine cycles...

Keep in mind that in certain situations interrupt needs to be disabled, by clearing EX0 (or also EX1) bit, and that this should be done inside interrupt service routine (ISR).

Kai