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/* ----------------------------------------------------------------------------

 *         ATMEL Microcontroller Software Support

 * ----------------------------------------------------------------------------

 * Copyright (c) 2008, Atmel Corporation

 *

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 * - Redistributions of source code must retain the above copyright notice,

 * this list of conditions and the disclaimer below.

 *

 * Atmel's name may not be used to endorse or promote products derived from

 * this software without specific prior written permission.

 *

 * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE

 * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,

 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,

 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 * ----------------------------------------------------------------------------

 */

//------------------------------------------------------------------------------

//         Headers

//------------------------------------------------------------------------------

#include "tc.h"

//------------------------------------------------------------------------------

//         Global functions

//------------------------------------------------------------------------------

//------------------------------------------------------------------------------

/// Configures a Timer Counter to operate in the given mode. Timer is stopped

/// after configuration and must be restarted with TC_Start().

/// to obtain the target frequency.

/// \param pTc  Pointer to an AT91S_TC instance.

/// \param mode  Operating mode.

//------------------------------------------------------------------------------

void TC_Configure(AT91S_TC *pTc, unsigned int mode)

{

    // Disable TC clock

    pTc->TC_CCR = AT91C_TC_CLKDIS;

    // Disable interrupts

    pTc->TC_IDR = 0xFFFFFFFF;

    // Clear status register

    pTc->TC_SR;

    // Set mode

    pTc->TC_CMR = mode;

}

//------------------------------------------------------------------------------

/// Starts the timer clock.

/// \param pTc  Pointer to an AT91S_TC instance.

//------------------------------------------------------------------------------

void TC_Start(AT91S_TC *pTc)

{

    pTc->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;

}

//------------------------------------------------------------------------------

/// Stops the timer clock.

/// \param pTc  Pointer to an AT91S_TC instance.

//------------------------------------------------------------------------------

void TC_Stop(AT91S_TC *pTc)

{

    pTc->TC_CCR = AT91C_TC_CLKDIS;

}

//------------------------------------------------------------------------------

/// Finds the best MCK divisor given the timer frequency and MCK. The result

/// is guaranteed to satisfy the following equation:

///   (MCK / (DIV * 65536)) <= freq <= (MCK / DIV)

/// with DIV being the highest possible value.

/// Returns 1 if a divisor could be found; otherwise returns 0.

/// \param freq  Desired timer frequency.

/// \param mck  Master clock frequency.

/// \param div  Divisor value.

/// \param tcclks  TCCLKS field value for divisor.

//------------------------------------------------------------------------------

unsigned char TC_FindMckDivisor(

    unsigned int freq,

    unsigned int mck,

    unsigned int *div,

    unsigned int *tcclks)

{

    const unsigned int divisors[5] = {2, 8, 32, 128,

#if defined(at91sam9260) || defined(at91sam9261) || defined(at91sam9263) \

    || defined(at91sam9xe) || defined(at91sam9rl64) || defined(at91cap9)

        BOARD_MCK / 32768};

#else

        1024};

#endif

    unsigned int index = 0;

    // Satisfy lower bound

    while (freq < ((mck / divisors[index]) / 65536)) {

        index++;

        // If no divisor can be found, return 0

        if (index == 5) {

            return 0;

        }

    }

    // Try to maximise DIV while satisfying upper bound

    while (index < 4) {

        if (freq > (mck / divisors[index + 1])) {

            break;

        }

        index++;

    }

    // Store results

    if (div) {

        *div = divisors[index];

    }

    if (tcclks) {

        *tcclks = index;

    }

    return 1;

}