编码器程序。运行后TIM_Counter(TIM3)得不到数值是为什么

下面是我按网上的例程改写的旋转编码器角度的计算程序，用定时器计数值来计算角度，利用tiM_Counter(TIM3)来得到TIM3的计数值，然后用来算旋转角。编译没有出错，但是单步运行时会发现TIMX为0x40000400,但是jishu，temp，angle都是0，这是为什么？
求指教！谢谢

#include "timer.h"
#include "usart.h"
#include "STM32f10x_tim.h"
#include "sys.h"

void TIM_Init(void)   
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_ICInitTypeDef TIM_ICInitStructure;  
NVIC_InitTypeDef NVIC_InitStructure;   
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;   
  GPIO_Init(GPIOC, &GPIO_InitStructure);     

NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;  
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM_DeInit(TIM3);

TIM_TimeBaseStructure.TIM_Period = 999;
TIM_TimeBaseStructure.TIM_Prescaler =0x00;  
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  TIM_EncoderInterfaceConfig(TIM3,TIM_EncoderMode_TI12,TIM_ICPolarity_Rising,TIM_ICPolarity_Rising);
  TIM_ICStructInit(&TIM_ICInitStructure);
  TIM_ICInitStructure.TIM_ICFilter=0x03;
  TIM_ICInit(TIM3,&TIM_ICInitStructure);

TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE );
TIM_ClearFlag(TIM3,TIM_FLAG_Update);
TIM3->CNT=0;

TIM_Cmd(TIM3, ENABLE);  
}
s32 Get_Angle(void)
{
s32 temp;
s32 angle;
s32 jishu;
jishu=TIM_GetCounter(TIM3);
temp=(jishu)*360/1000;
angle=temp/65536;
return angle;
}
void TIM3_IRQHandler(void)
{
if(TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)
{
  TIM_ClearFlag(TIM3,TIM_FLAG_Update);
  TIM_ClearITPendingBit(TIM3, TIM_IT_Update);  
}
}