Vojtech,
You can find it in all the reference manuals (K10-K70). In the K10P81M100SF2RM, you can see it in Figure 32-1, as the "compare logic" at the bottom of the image. These are described in section 32.3.5. The ACFE, ACFGT and ACREN bits in ADCx_SC2 turn on and off the compare functions of the part (32.3.6).
The operation is described in 32.4.6. The COCO only is triggered if the compare condition is true.
Thanks!
Josh E