void pit_init(uint8 pitno,uint32 timeout)
{
SIM_SCGC6|=SIM_SCGC6_PIT_MASK; //使能PIT时钟
PIT_MCR&=~(PIT_MCR_MDIS_MASK); //调试模式下禁止
PIT_MCR|=PIT_MCR_FRZ_MASK; //使能PIT模块时钟
PIT_LDVAL(pitno)=timeout; //设置周期
PIT_TCTRL(pitno)|=PIT_TCTRL_TEN_MASK; //使能pit模块运行
PIT_TCTRL(pitno)&=~(PIT_TCTRL_TIE_MASK); //关pit中断
}
/*************************************************************************
* 野火嵌入式開發工作室
*
* 函數名稱：pit_init
* 功能說明：PITn定時中斷
* 參數說明：PITn 模塊號（PIT0~PIT3）
cnt 延時時間(單位為bus時鐘周期)
* 函數返回：無
* 修改時間：2012-1-24
* 備 注：
*************************************************************************/
void pit_init(PITn pitn,u32 cnt)
{
//PIT 用的是 Bus Clock 總線頻率
//溢出計數 = 總線頻率 * 時間
/* 開啟時鐘*/
SIM_SCGC6 |=SIM_SCGC6_PIT_MASK; //使能PIT時鐘
/* PIT模塊控制 PIT Module Control Register (PIT_MCR) */
PIT_MCR &=~(PIT_MCR_MDIS_MASK | PIT_MCR_FRZ_MASK ); //使能PIT定時器時鐘 ，調試模式下繼續運行
/* 定時器加載值設置 Timer Load Value Register (PIT_LDVALn) */
PIT_LDVAL(pitn) =cnt; //設置溢出中斷時間
//定時時間到了後，TIF 置 1 。寫1的時候就會清0
PIT_Flag_Clear(pitn); //清中斷標志位
/* 定時器控制寄存器 Timer Control Register (PIT_TCTRL0) */
PIT_TCTRL(pitn) |=( PIT_TCTRL_TEN_MASK | PIT_TCTRL_TIE_MASK ); //使能 PITn定時器,並開PITn中斷
enable_irq(pitn+68); //開接收引腳的IRQ中斷
}
/*******************************************************************************
* void pit_init(uint32_t pit, uint32_t frq, uint32_t interrupt)
*
* Description:
* Initialize specified periodic interrupt timer (PIT) with specified
* repetition frequency.
*
* Parameters:
* pit PIT channel to be initialized (PIT0, PIT1, PIT2, PIT3)
* frq PIT repetition frequency in Hz
* interrupt PIT interrupt generation (ENABLE_INT, DISABLE_INT)
*
* Return:
* none
*
* Example:
* pit_init(PIT0, 1000000, ENABLE_INT);
* Initialize PIT0 with a repetition frequency of 1000000 Hz. After the
* expiration of a period, PIT0 interrupt service routine calls PIT0 callback
* function.
*
* Notes:
* PIT module is clocked by bus clock.
*
* History:
* pka, 27/AUG/2014, removed automatic start of PIT module
* pka, 25/MAR/2014, initial code
*******************************************************************************/
void pit_init(uint32_t pit, uint32_t frq, uint32_t interrupt)
{
/* Enable PIT module clock. */
SIM_SCGC6 |= SIM_SCGC6_PIT_MASK;
/* Enable PIT module. PIT_MCR[MDIS] bit MUST be enabled before any other
* bit manipulation is done. */
PIT_MCR &= ~PIT_MCR_MDIS_MASK;
/* Set timer start value. The timer counts down until it reaches 0. When 0
* is reached an interrupt will be generated. */
PIT_LDVAL(pit) = PIT_CLK / frq - 1;
/* Check if interrupts are enabled. */
if (interrupt)
{
/* Enable timer interrupt. */
PIT_TCTRL(pit) |= PIT_TCTRL_TIE_MASK;
/* Enable PIT interrupt. */
enable_int(INT_PIT);
}
}
/*******************************************************************************
* void pit_set(uint32_t pit, uint32_t frq)
*
* Description:
* Set repetition frequency of specified periodic interrupt timer (PIT).
*
* Parameters:
* pit PIT channel to be set
* frq PIT repetition frequency in Hz
*
* Return:
* actual PIT repetition frequency
*
* Example:
* pit0_frq = pit_set(PIT0, 1000000);
* Set PIT0 repetition frequency and get actual frequency value.
*
* Notes:
* According to the specified PIT frequency the timer start value is
* calculated. The calculation of this start value contains a division. Since
* the start value is loaded to a 32-bit register this may cause rounding
* errors and subsequently a wrong PIT repetition frequency.
*
* History:
* pka, 11/SEP/2014, initial code
*******************************************************************************/
void pit_set(uint32_t pit, uint32_t frq)
{
/* Set timer start value. */
PIT_LDVAL(pit) = PIT_CLK / frq - 1;
}
