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제가 c공부중 타이머 부분을 공부하게됐는데 아직 모르는게 많아서
주석을 달면서 공부중인데 모르는 부분이있어서 아시는분은 주석좀...

/*---------------------------------------------------------------------------------------------------------*/
/* Function: GetTimerClock */
/* */
/* Parameters: */
/* ch - [in] */
/* E_TIMER_CHANNEL, it could be E_TMR0/E_TMR1/E_TMR2/E_TMR3 */
/* Returns: */
/* u32clk The timer clock (Hz) */
/* E_DRVTIMER_CHANNEL Invalid Timer channel */
/* E_DRVTIMER_CLOCK_RATE Invalid Timer clock source */
/* Description: */
/* Get the timer clock from the specified timer channel. */
/*---------------------------------------------------------------------------------------------------------*/
static uint32_t GetTimerClock(E_TIMER_CHANNEL ch)
{
volatile uint8_t u8ClockSrc;
volatile uint32_t u32clk = 0;

if ((ch == E_TMR0) || (ch == E_TMR1) || (ch == E_TMR2) || (ch == E_TMR3))
{
u8ClockSrc = (inpw(&SYSCLK-CLKSEL1) (8+(ch*4))) & 0x7;
if (u8ClockSrc == 0)
{
u32clk = DrvSYS_GetExtClockFreq() ; /* Option 0: Get External Clock From DrvSYS Setting */
}
else if(u8ClockSrc == 1)
{
u32clk = __RTC_XTAL; /* Option 1: 32K */
}
else if(u8ClockSrc == 2)
{
u32clk = DrvSYS_GetHCLKFreq(); /* Option 2: HCLK */
}
else if(u8ClockSrc == 7)
{
u32clk = __IRC22M;p; /* Option 7: 22MHz*/
}else
{
return E_DRVTIMER_CLOCK_RATE;
}
}
else
return E_DRVTIMER_CHANNEL;

return u32clk;
}
/*---------------------------------------------------------------------------------------------------------*/
/* Function: CalTimerInitValue */
/* */
/* Parameters: */
/* u32ClockValue - [in] */
/* Input the clock value of Timer */
/* u32TicksPerSec - [in] */
/* Specify the ticks per second of Timer */
/* Returns: */
/* Return 32 bits unsigned integer where */
/* bits [ 0:23] - The Timer Compare Value(TCMPR) for Timer */
/* bits [24:31] - The pre-scale value for Timer */
/* (uint32_t)-1 Out of range */
/* Description: */
/* Calculate the Timer Compare Value and pre-scale value for Timer */
/*---------------------------------------------------------------------------------------------------------*/
static uint32_t CalTimerInitValue(uint32_t u32ClockValue, uint32_t u32TicksPerSec)
{
uint32_t u32PreScale;
uint32_t u32TCMPRValue;
if ((u32ClockValue 2) || (u32TicksPerSec == 0))
return (uint32_t)-1;
for (u32PreScale=1; u32PreScale256; u32PreScale++)
{
u32TCMPRValue = u32ClockValue / (u32TicksPerSec * u32PreScale);
/* The TCMPR value must 1 */
if ((u32TCMPRValue 1) && (u32TCMPRValue 0x1000000))
return (((u32PreScale-1) 24) | u32TCMPRValue);
}

return (uint32_t)-1;
}

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