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/* ----------------------------------------------------------------------------
* ATMEL Microcontroller Software Support
* ----------------------------------------------------------------------------
* Copyright (c) 2009, 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.
* ----------------------------------------------------------------------------
*/
/**
* \file
*
* Implementation of Timer Counter (TC).
*
*/
/*------------------------------------------------------------------------------
* Headers
*------------------------------------------------------------------------------*/
#include "chip.h"
#include <assert.h>
/*------------------------------------------------------------------------------
* Global functions
*------------------------------------------------------------------------------*/
/**
* \brief Configures a Timer Counter Channel
*
* Configures a Timer Counter to operate in the given mode. Timer is stopped
* after configuration and must be restarted with TC_Start(). All the
* interrupts of the timer are also disabled.
*
* \param pTc Pointer to a Tc instance.
* \param channel Channel number.
* \param mode Operating mode (TC_CMR value).
*/
extern void TC_Configure( Tc *pTc, uint32_t dwChannel, uint32_t dwMode )
{
TcChannel* pTcCh ;
assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
pTcCh = pTc->TC_CHANNEL+dwChannel ;
/* Disable TC clock */
pTcCh->TC_CCR = TC_CCR_CLKDIS ;
/* Disable interrupts */
pTcCh->TC_IDR = 0xFFFFFFFF ;
/* Clear status register */
pTcCh->TC_SR ;
/* Set mode */
pTcCh->TC_CMR = dwMode ;
}
/**
* \brief Reset and Start the TC Channel
*
* Enables the timer clock and performs a software reset to start the counting.
*
* \param pTc Pointer to a Tc instance.
* \param dwChannel Channel number.
*/
extern void TC_Start( Tc *pTc, uint32_t dwChannel )
{
TcChannel* pTcCh ;
assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
pTcCh = pTc->TC_CHANNEL+dwChannel ;
pTcCh->TC_CCR = TC_CCR_CLKEN | TC_CCR_SWTRG ;
}
/**
* \brief Stop TC Channel
*
* Disables the timer clock, stopping the counting.
*
* \param pTc Pointer to a Tc instance.
* \param dwChannel Channel number.
*/
extern void TC_Stop(Tc *pTc, uint32_t dwChannel )
{
TcChannel* pTcCh ;
assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
pTcCh = pTc->TC_CHANNEL+dwChannel ;
pTcCh->TC_CCR = TC_CCR_CLKDIS ;
}
/**
* \brief Find best MCK divisor
*
* Finds the best MCK divisor given the timer frequency and MCK. The result
* is guaranteed to satisfy the following equation:
* \code
* (MCK / (DIV * 65536)) <= freq <= (MCK / DIV)
* \endcode
* with DIV being the highest possible value.
*
* \param dwFreq Desired timer frequency.
* \param dwMCk Master clock frequency.
* \param dwDiv Divisor value.
* \param dwTcClks TCCLKS field value for divisor.
* \param dwBoardMCK Board clock frequency.
*
* \return 1 if a proper divisor has been found, otherwise 0.
*/
extern uint32_t TC_FindMckDivisor( uint32_t dwFreq, uint32_t dwMCk, uint32_t *dwDiv, uint32_t *dwTcClks, uint32_t dwBoardMCK )
{
const uint32_t adwDivisors[5] = { 2, 8, 32, 128, dwBoardMCK / 32768 } ;
uint32_t dwIndex = 0 ;
/* Satisfy lower bound */
while ( dwFreq < ((dwMCk / adwDivisors[dwIndex]) / 65536) )
{
dwIndex++ ;
/* If no divisor can be found, return 0 */
if ( dwIndex == (sizeof( adwDivisors )/sizeof( adwDivisors[0] )) )
{
return 0 ;
}
}
/* Try to maximize DIV while satisfying upper bound */
while ( dwIndex < 4 )
{
if ( dwFreq > (dwMCk / adwDivisors[dwIndex + 1]) )
{
break ;
}
dwIndex++ ;
}
/* Store results */
if ( dwDiv )
{
*dwDiv = adwDivisors[dwIndex] ;
}
if ( dwTcClks )
{
*dwTcClks = dwIndex ;
}
return 1 ;
}
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