F2812：将关键代码从闪存迁移到RAM提升运行效率

例程： 
第一步：

// Functions that will be run from RAM need to be assigned to
// a different section.  This section will then be mapped using
// the linker cmd file.
#pragma CODE_SECTION(EPwm1_timer_isr, "ramfuncs");
#pragma CODE_SECTION(EPwm2_timer_isr, "ramfuncs");

MAIN()
{
// These are defined by the linker (see F2808.cmd)在CMD里面定义的变量
extern Uint16 RamfuncsLoadStart;
extern Uint16 RamfuncsLoadEnd;
extern Uint16 RamfuncsRunStart;

User specific code, enable interrupts:

// Copy time critical code and Flash setup code to RAM
// This includes the following ISR functions: EPwm1_timer_isr(), EPwm2_timer_isr()
// EPwm3_timer_isr and and InitFlash();
// The  RamfuncsLoadStart, RamfuncsLoadEnd, and RamfuncsRunStart
// symbols are created by the linker. Refer to the F2808.cmd file.
   MemCopy(&RamfuncsLoadStart, &RamfuncsLoadEnd, &RamfuncsRunStart);

// Call Flash Initialization to setup flash waitstates
// This function must reside in RAM
   InitFlash();//FLASH初始化的函数不能在FLASH里面运行，必须拷到别的内存空间里运行才能对FLASH进行初始化。
}