关于 hall 时间检测问题

if(gHall_State != gHall_PrevState)
 {
  gHall_timer_now = HAL_readTimerCnt(halHandle,2);      定时器2 

  gHall_time_delta_now = gHall_timer_prev – gHall_timer_now;
  gHall_timer_prev = gHall_timer_now;

  gHall_time_delta = (gHall_time_delta_now + gHall_time_delta_prev)>>1;
  gHall_time_delta_prev = gHall_time_delta_now;

  gHall_speed_fdb_0p01Hz = gHall_speed_scale/gHall_time_delta;
  gHall_speed_fdb_pu = gHall_speed_fdb_0p01Hz*gHall_Speed_0p01hzto_pu_sf;

proj-lab11e 历程中

用上个hall的   定时器2 的只 减去 本次hall    定时器2的值， 如果 上次的值小于本次的值， 那么 计算不是错了吗？