- /**
- * [url=home.php?mod=space&uid=247401]@brief[/url] Open Timer in specified mode and frequency
- *
- * @param[in] timer The base address of Timer module. It could be TIMER0, TIMER1, TIMER2, TIMER3.
- * @param[in] u32Mode Operation mode. Possible options are
- * - \ref TIMER_ONESHOT_MODE
- * - \ref TIMER_PERIODIC_MODE
- * - \ref TIMER_TOGGLE_MODE
- * - \ref TIMER_CONTINUOUS_MODE
- * @param[in] u32Freq Target working frequency
- *
- * [url=home.php?mod=space&uid=266161]@return[/url] Real Timer working frequency
- *
- * [url=home.php?mod=space&uid=1543424]@Details[/url] This API is used to configure timer to operate in specified mode and frequency.
- * If timer cannot work in target frequency, a closest frequency will be chose and returned.
- * [url=home.php?mod=space&uid=536309]@NOTE[/url] After calling this API, Timer is \b NOT running yet. But could start timer running be calling
- * \ref TIMER_Start macro or program registers directly.
- */
- uint32_t TIMER_Open(TIMER_T *timer, uint32_t u32Mode, uint32_t u32Freq)
- {
- uint32_t u32Clk = TIMER_GetModuleClock(timer);
- uint32_t u32Cmpr = 0, u32Prescale = 0;
- // Fastest possible timer working freq is (u32Clk / 2). While cmpr = 2, pre-scale = 0.
- if(u32Freq > (u32Clk / 2))
- {
- u32Cmpr = 2;
- }
- else
- {
- if(u32Clk >= 0x4000000)
- {
- u32Prescale = 7; // real prescaler value is 8
- u32Clk >>= 3;
- }
- else if(u32Clk >= 0x2000000)
- {
- u32Prescale = 3; // real prescaler value is 4
- u32Clk >>= 2;
- }
- else if(u32Clk >= 0x1000000)
- {
- u32Prescale = 1; // real prescaler value is 2
- u32Clk >>= 1;
- }
- u32Cmpr = u32Clk / u32Freq;
- }
- timer->TCSR = u32Mode | u32Prescale;
- timer->TCMPR = u32Cmpr;
- return(u32Clk / (u32Cmpr * (u32Prescale + 1)));
- }
* @param[in] u32Freq Target working frequency
*
* @return Real Timer working frequency
好多人疑问的是这两个，也就是第三个参数和返回值，其实一个是目标值，一个是实时值，也就是你想设置的是什么，实际上设置后是什么
| 
楼主
