DC电机pwm控制factor除1024是为什么，factor*1000又是啥，如果-1000呢

int factor = DCM_TCNTB0/1024;
if((dcm_fd=::open(DCM_DEV, O_WRONLY))<0){
printf("Error opening %s device\n", DCM_DEV);
}

    if(flag==0)
     {
          ::ioctl(dcm_fd, DCM_IOCTRL_SETPWM, (1000 * factor));

先了解各个变量的意义和ioctl接口的参数定义，这么一点，外人没法分析