Hi
The BC function generates the DC-bus break control signal based on the actual DC-bus voltage.
So the u_dc_bus_ON and u_dc_bus_OFF thresholds have to be properly set and also actual DC-bus voltage have to be measured and passed to BC function following BC update. Check if all above is done properly.
The usage of the BC eTPU function is demonstrated in the application “BLDC Motor with Speed Closed Loop and DC-Bus Break Controller”. For a detailed description of the demo refer to AN2954 (http://cache.freescale.com/files/32bit/doc/app_note/AN2954.pdf).
Regards,
Petr