請問下這段代碼，通用定時器2，設置中心對齊PWM模式1，我設置ARR寄存器為10*1000，分頻系數為5*1000，為什么出來的方波周期卻是2S的？
/*系統時鐘頻率為50MHZ*/
RCC->CFGR |= 4 << 10;
RCC->APB1ENR |= 1;/*使能TIM2時鐘*/
TIM2->CR1 = 0;
TIM2->CR1 |= 1 << 7;/*ARPE,開啟預裝載寄存器緩沖*/
TIM2->CR1 |= (0x01 << 5);/*CMS: Center-aligned mode selection set to 01: Center-aligned mode 1 the counter counts down.*/
/*計數器50MHZ == 每秒50 * 1000 * 1000次，分頻系數為5000（從0開始所以要減一），故每秒10 * 1000等于一萬次*/
TIM2->ARR = 10000;/*預裝載寄存器*/
TIM2->DIER |= 1;//使能更新中斷
TIM2->PSC = 5000 - 1;/*設置定時器分頻系數*/
TIM2->CCMR1 = 0;
TIM2->CCMR1 |= 1 << 3;/*OC1PE使能preload register*/
TIM2->CCMR1 |= 6 << 4;/*OC1M Output compare 1 mode set to PWM mode 1*/
TIM2->CCMR1 &= ~0x3;/*CC1 channel is configured as output*/
TIM2->CCR1 = 2500;/*產生一個占空比為百分之25（2500 / 10000）的PWM波*/
TIM2->CCER = 0;
TIM2->CCER |= 1;/*CC1E: Capture/Compare 1 output enable*/
TIM2->CR1 |= 1; /*使能定時器*/
TIM2->EGR |= 1;/*產生UG更新事件*/
TIM2->SR &= ~((u32)1);
/*PA15-->TIM2_CH1配置*/
RCC->AHB1ENR |= 1;/*使能GPIOA時鐘源*/
/*初始化GPIOA的IO口配置*/
/*PA0為輸出(系統默認推挽就不配置了)*/
GPIOA->MODER |= ((u32)2 << 2 * 15);/*PA15配置為復用*/
GPIOA->AFR[1] = 0;
GPIOA->AFR[1] = 1 << 4 * 7;//AFRH15 AF1
圖中每個格子為1S
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