Hi Lion-o, well I have not problem using the gp timers, in fact I solved the issue using timer 1. However, the reason to choose BF-537 was because I need to measure time in interval of 3 nsec more less and the core timer at 600Mhz os CCLK can do this. I received information about lv Blackfin team of the core timer is used by VDK, so I wondering why there VIs to control the core timer in LV Blackfin if it is used by VDK?