Hello Mehmet,
Have you followed both notes in section 22.3.1 in the Vybrid reference manual? I am unsure if your code:
DMAMUX0_CHCFG2 = DMAMUX_CHCFG_SOURCE(13) | DMAMUX_CHCFG_ENBL_MASK;
will work due to the note, "Before changing the trigger or source settings, a DMA channel must be disabled via the CHCFGn[ENBL] bit.". Try disabling the CHCFGn[ENBL] bit, set the source, then enable the CHCFGn[ENBL] bit.
Thanks,
Timesys Support