TMS570LC4357: eCap clock to calculate period

Hei,

I would like to know with what clock works the eCap so that I can calculate the period of the signal? I read in the reference manual that the 32-bit counter is clocked via the system clock and I see in the Halcogen example of eCap that VCLK3_FREQ is used to calculate the period, but when using  it in my program this  VCLK3_FREQ is not recognized (I'm not using epwm as in the example) so I'm not sure what reference to use to calculate the period.

In the Halcogen example this formula is used:

period = (cap3 - cap1)*1000/VCLK3_FREQ;

Thanks a lot.