If you need exact duty cycles this will not work. Example: 13kHz == 769.2 x 100nsec you choose 769

256/13=19.7 --> 769/19.7=39.05 you choose 39 / 730

High Speed mode:

in interrupt pseudo code:

if(P1_3) {
CCAP0 += 730; // direct addition will not work!
wNextCCAP0=CCAP0+39;
} else {
CCAP0 += 39; // you may have a time problem here
}

this will produce your desired 13/243 duty cycle on Port 1.3

you can enhance the timing like this:

if(P1_3) {
CCAP0 += 730; // direct addition will not work!
wNextCCAP0=CCAP0+39;
} else {
CCAP0=wNextCCAP0;
}

you may still have a timing problem here, since interrupt routine needs a couple of usecs

Werner