settimer34period.c

传感器网络CC2430模块开发,IEEE802.15.4 MAC 协议实现源程序.

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Filename:     setTimer34Period.c
Target:       cc2430
Author:       EFU
Revised:      1/3-2007
Revision:     1.1
******************************************************************************/
#include "hal.h"


//------------------------------------------------------------------------------------------------------
// See hal.h for a description of this function.
//------------------------------------------------------------------------------------------------------
BYTE halSetTimer34Period(BYTE timer, DWORD period){
  BYTE div = 0;

  if(TICKSPD > 5) { // Checking that the period is not too short.
    if( (period < 2*(TICKSPD-5)) && (period != 0) ){
      return 0;
    }
  }

  if(period == 0){  // If period is 0, max period length and max prescaler
    div = 7;  // division is used.
    period = 255;
  } else {
    period = ((period*32) >> TICKSPD);// Determining how many timer ticks the period consist of
    while(period > 255){              // If the period is too long, the prescaler division is
      period = (period >> 1);   // increased.
      div++;
      if(div > 7){              // If the period is too long when using max prescaler division,
        return 0;         // 0 is returned.
      }
    }
  }

  if(timer == 4){
    // Timer 4 selected
    T4CTL |= (div << 5);              // Setting prescaler value
    T4CC0 = (BYTE) period;            // Setting timer value.
  } else if(timer == 3){
    // Timer 3 selected
    T3CTL |= (div << 5);              // Setting prescaler value
    T3CC0 = (BYTE) period;            // Setting timer value.
  } else {
    return 0;
  }

  return period;
}