thanx for all the help maarten. u have certainly helped a lot. i think i am actually measuring movement now!

i just want to know if im doing things right. i am going to include some definitions and my ISR below.

// definitions
sbit DX = P0^6; // define PWM port pin - [DOUTX on accelerometer]
sbit DY = P0^7; // define PWM port pin - [DOUTY on accelerometer]

unsigned int xVal1, xVal2, pulseX1, pulseX2, xMove;

char XReading1 = 1; // this only so i know when i have taken first pulse width and when i have taken 2nd pulse width

void PCA_ISR (void) interrupt 9
{
if (CCF0) {

if (DX) { // process rising edge

xVal1 = PCA0CPL0;
xVal1 += PCA0CPH0<<8;

} else { // process falling edge

xVal2 = PCA0CPL0;
xVal2 += PCA0CPH0<<8;

if (XReading1)
{
pulseX1 = xVal2 - xVal1; // 1st pulse width
} else {
pulseX2 = xVal2 - xVal1; // 2nd pulse width
}

if (!XReading1)
{
// when subtracting 2 pulse widths from each other
// you will measure movement, according to
// man-down PDF i read
xMove = abs(pulseX1 - pulseX2);
}

XReading1 = !XReading1;

}

CCF0 = 0; // clear compare indicator

} else if (CF) {
CF = 0;
}
}

when i have no motion, the xMove value never goes above 17, as soon as i move the board around, it goes above that. so i must be measuring movement.

i just want to know if im doing this correctly.

another thing, CEX1 which is on PO.7, i also use PCA0CP0 to measure the pulse width? i added DY in the ISR using the same code as i do for DX, just naming the variables as 'y' where neccesary, and when moving the board around, i do get different values on xMove & yMove.