lab11e中的一段程序，修改之后实现电机反转

gHall_State_delta = gHall_PwmIndex[gHall_State] - gHall_PwmIndex[gHall_PrevState];

  if((gHall_State_delta == -1) || (gHall_State_delta == 5))
  {
   gHall_dir = 1;   // positive direction
  }
     else if((gHall_State_delta == 1) || (gHall_State_delta == -5))
  {
   gHall_dir = 2;   // negative direction
   gHall_speed_fdb_pu = -gHall_speed_fdb_pu;
  }
  else
  {
   gHall_dir = 0;   // direction change
  }

这是lab11e中的一段程序，上面是变量地址的计算，目前是正转，我修改了gHall_State_delta = gHall_PwmIndex[gHall_PrevState] - gHall_PwmIndex[gHall_State];按照程序可以实现反转，但是还是正转，为什么呢？