STM32F103ZET6里共有8個定時器，其中高級定時器有TIM1-TIM5、TIM8，共6個。

這里需要使用定時器的級聯(lián)功能，ST的RM0008 REV12的P388和P399頁上有說明對于特定的定時器，怎么去選擇級聯(lián)功能，參見表86。

我這里輸出PWM的定時器是TIM2，空閑的定時器是TIM3。以TIM2為主定時器，TIM3為從定時器對TIM2的輸出脈沖數(shù)進行計數(shù)。

查表可知，TIM3為從定時器選擇TIM2為觸發(fā)源，需要配置TS=001，即選擇ITR1。

實現(xiàn)通過定時器控制輸出PWM個數(shù)的功能，可以有如下一種配置方式：

void TIM2_Master__TIM3_Slave_Configuration(u32 PulseFrequency)

{

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;

u16 nPDTemp ;

/* -----------------------------------------------------------------------

TIMx Configuration: generate 4 PWM signals with 4 different duty cycles:

TIMxCLK = 72 MHz, Prescaler = 0x0, TIMx counter clock = 72 MHz

TIMx ARR Register = 0 => TIMx Frequency = TIMx counter clock/(ARR + 1)

TIMx Frequency = 72MHz.

----------------------------------------------------------------------- */

TIM_Cmd(TIM2, DISABLE);

nPDTemp = 72000000UL/PulseFrequency;

// 時基配置：配置PWM輸出定時器——TIM2

/* Time base configuration */

TIM_TimeBaseStructure.TIM_Period = nPDTemp-1;

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_ClockDivision = 0;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

// 輸出配置：配置PWM輸出定時器——TIM2

/* PWM1 Mode configuration: Channel1 */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = nPDTemp>>1;//50%

TIM_OC1Init(TIM2, &TIM_OCInitStructure);

TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);

// 時基配置：配置脈沖計數(shù)寄存器——TIM3

TIM_TimeBaseStructure.TIM_Period = 0xFFFF;

TIM_TimeBaseStructure.TIM_Prescaler = 1;

TIM_TimeBaseStructure.TIM_ClockDivision = 0;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

/* Output Compare Active Mode configuration: Channel1 */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Inactive;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = 0xFFFF; // 這里的配置值意義不大

TIM_OC1Init(TIM3, &TIM_OCInitStructure);

// 配置TIM2為主定時器

/* Select the Master Slave Mode */

TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);

/* Master Mode selection */

TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);

// 配置TIM3為從定時器

/* Slave Mode selection: TIM3 */

TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Gated);

TIM_SelectInputTrigger(TIM3, TIM_TS_ITR1);

TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);

TIM_Cmd(TIM2, DISABLE);

TIM_Cmd(TIM3, DISABLE);

}

中斷服務(wù)程序如下：

u8 TIM2_Pulse_TIM3_Counter_OK = 0;

void TIM3_IRQHandler(void)

{

if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)

{

TIM_ClearITPendingBit(TIM3, TIM_IT_CC1); // 清除中斷標(biāo)志位

TIM_Cmd(TIM2, DISABLE); // 關(guān)閉定時器

TIM_Cmd(TIM3, DISABLE); // 關(guān)閉定時器

TIM2_Pulse_TIM3_Counter_OK = 1;

}

}

應(yīng)用程序為：

u16 pulsecnt = 10000;

void main(void)

{

SystemSetup(); // 初始化內(nèi)核和外設(shè)

TIM2_Master__TIM3_Slave_Configuration(10000);//配置TIM2的脈沖輸出為10k

while(1)

{

TIM_ITConfig(TIM3, TIM_IT_CC1, DISABLE); /* TIM enable counter */

TIM_Cmd(TIM3, ENABLE);

TIM3->CCR1 = pulsecnt;

TIM3->CNT = 0;

TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);

TIM_Cmd(TIM2, ENABLE); /* TIM enable counter */

while(TIM2_Pulse_TIM3_Counter_OK == 0);

}

}

這種配置方式下，使用的是TIM3的比較中斷，我還沒試驗過其他的方式，想來應(yīng)該也是可以的，比如用定時器更新中斷……