28335之定时器原理

单片机的定时器就很简单，28335的定时器也没难道那里去。参考文章《https://blog.csdn.net/hmf1235789/article/details/51891997》

涉及经常使用的就一个time0定时器，其他两个不用。用的话，原理也一样。

涉及time0的寄存器也就5个：TDDRH:TDDR                   PSCH:PSC

                                               PRDH :PRD                      TIMH:TIM

还有一个crl寄存器，主要管理中断控制类的，在此不细说。看上边4个寄存器，其实用得就两个，而且一个还经常是0.

TDDRH:TDDR  ：作用将系统时钟分频（降低频率），供定时器用。经常设置为0

PRDH :PRD ：查数用的

PSCH:PSC  和  TIMH:TIM分别装载以上连个寄存器的数据；PSCH:PSC 减到0之后发出一个时钟信号给TIMH:TIM，然后自动装载TDDRH:TDDR。

TIMH:TIM 减到0之后，发出一个中断信号，然后自动装载PRDH :PRD

如何计算：参考《手把手教你学DSP2812》里边的解释很清晰

提醒：

CpuTimer0.RegsAddr = &CpuTimer0Regs;

是什么？

（cputime.c的代码）

struct CPUTIMER_VARS CpuTimer0;

// CpuTimer 1 and CpuTimer2 are used by DSP BIOS & other RTOS. Comment out if using DSP BIOS or other RTOS.
struct CPUTIMER_VARS CpuTimer1;
struct CPUTIMER_VARS CpuTimer2;

//---------------------------------------------------------------------------
// InitCpuTimers:
//---------------------------------------------------------------------------
// This function initializes all three CPU timers to a known state.
//
void InitCpuTimers(void)
{
    // CPU Timer 0
	// Initialize address pointers to respective timer registers:
	CpuTimer0.RegsAddr = &CpuTimer0Regs;
	// Initialize timer period to maximum:
	CpuTimer0Regs.PRD.all  = 0xFFFFFFFF;
	// Initialize pre-scale counter to divide by 1 (SYSCLKOUT):
	CpuTimer0Regs.TPR.all  = 0;
	CpuTimer0Regs.TPRH.all = 0;
	// Make sure timer is stopped:
	CpuTimer0Regs.TCR.bit.TSS = 1;
	// Reload all counter register with period value:
	CpuTimer0Regs.TCR.bit.TRB = 1;
	// Reset interrupt counters:
	CpuTimer0.InterruptCount = 0;

cputime.h的代码

struct CPUTIMER_REGS {
   union TIM_GROUP TIM;   // Timer counter register
   union PRD_GROUP PRD;   // Period register
   union TCR_REG   TCR;   // Timer control register
   Uint16          rsvd1; // reserved
   union TPR_REG   TPR;   // Timer pre-scale low
   union TPRH_REG  TPRH;  // Timer pre-scale high
};

//---------------------------------------------------------------------------
// CPU Timer Support Variables:
//
struct CPUTIMER_VARS {
   volatile struct  CPUTIMER_REGS  *RegsAddr;
   Uint32    InterruptCount;
   float   CPUFreqInMHz;
   float   PeriodInUSec;
};

//---------------------------------------------------------------------------
// Function prototypes and external definitions:
//
void InitCpuTimers(void);
void ConfigCpuTimer(struct CPUTIMER_VARS *Timer, float Freq, float Period);

extern volatile struct CPUTIMER_REGS CpuTimer0Regs;
extern struct CPUTIMER_VARS CpuTimer0;

// CpuTimer 1 and CpuTimer2 are reserved for DSP BIOS & other RTOS. Comment out CpuTimer1 and CpuTimer2 if using DSP BIOS or other RTOS
extern volatile struct CPUTIMER_REGS CpuTimer1Regs;
extern volatile struct CPUTIMER_REGS CpuTimer2Regs;

extern struct CPUTIMER_VARS CpuTimer1;
extern struct CPUTIMER_VARS CpuTimer2;