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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;
}
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