Hi, I may be too late to ask this as this thread is few years old, but I will take my chances.
I am trying to understand internal pull up on/off along with making sure pins are low before going to sleep.
If I wish the pins to be low when the program starts is it ok to use the statement: OPTION_REG=0 : GPIO=0
Since I am trying to understand internal pull up on/off so I will ask if there is any significance of OPTION_REG=128 over what I wrote above.

Secondly,
In the following code
Code:
Main:
    GPIO.0 = 1         ' set data latch on GPIO.0
    TRISIO.0 = 0       ' GPIO.0 = output (charging cap)
    PAUSEUS 24         ' charge cap for 24uS
    TRISIO.0 = 1       ' GPIO.0 = input to discharge cap
    IOCA.0 = 1         ' int on change enabled for GPIO.0
    INTCON = %00001000 ' global ints disabled, int on change enabled
    @ SLEEP            ' put PIC to sleep
    TOGGLE PROBE       ' indicate ULPWU wake up from sleep & clear mismatch
    INTCON.0 = 0       ' clear wake up on change int flag
    GOSUB TestVolts    ' go test for under voltage condition
    GOTO Main          ' not sure what this does...;o}
Suppose my port (Lets say sensor attached to GPIO.1) is held low and I want PIC to wake up once it goes high, does what its suppose to do, and when it again goes low PIC goes to sleep.
At what position in the code should I check to make sure port is LOW before PIC goes to sleep.

As lets say I put "WHILE gpio.1:wend" before capacitor is charged in the main loop, I fear that port could go high again while capacitor is getting charged and pic will go to sleep with the port being high.

If I put it after the capacitor charge statement, I fear the capacitor getting discharged while waiting for the port to go low which may take 1-2 seconds.

Hope I can have some help over the two issues. Thanks a lot