DRV10983: PWM cannot adjust motor speed

Hi Team,

#define REG_20 0x39
#define REG_21 0x38 
#define REG_22 0xAA
#define REG_23 0x08
#define REG_24 0x08 
#define REG_25 0xFD
#define REG_26 0x8B
#define REG_27 0xFC
#define REG_28 0x98
#define REG_29 0x77
#define REG_2A 0x05
#define REG_2B 0x02

The register configuration is as above. No matter how big the input PWM duty cycle is, the motor will always keep running at the highest speed. 

Writing 0X01 and 0X00 registers also cannot adjust the speed.

Reading 0X1E is always 0, no error reported.The value of 0X1B is consistent with the input PWM duty cycle. ReadING 0x20~0x2B, the register value is consistent with the written value.

Customer would like to know how to configure to adjust the motor speed?

Regards,

Annie