Problem for EVAL6482H

I have used EVAL6482H board to drive a stepper motor with a spec as followed,

Operating voltage: 2.5v

Rated current/ phase: 0.49A

Supply voltage: 20v

I set the parameter as followed

   Stepper.setParam(TVAL_HOLD, 0x02);

   Stepper.setParam(TVAL_RUN, 0x02);

   Stepper.setParam(OCD_TH, 0x08);

   Stepper.setParam(CONFIG, 0xF788);

   Stepper.setParam(GATECFG1, 0xC7);

   Stepper.setParam(GATECFG2, 0x61);

   Stepper.setParam(T_FAST, 0x47);

   Stepper.setParam(TON_MIN, 0x07);

   Stepper.setParam(TOFF_MIN, 0x1F);

However, the return value from getStatus is 0xE403 ( 1110 0100 0000 0011), which indicates the undervoltage lockout and the flag LED keep winkling.