sampling rate error in fpga design of brushless dc motor

i have designed fpga based speed control model of brushless dc motor in simulink. the controlling blocks used are from xilinx blocksets. and the pid controller is from DMC library. When I run the model I got the error that

 *The periodic sample time 1000000.0 is not allowed because the ratio of this sample time over base rate (1.0E-6) is greater than the maximum value of uint32.*

plz help me