/* ---------------------------------------------------------------------------- | |
* 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 | |
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* ---------------------------------------------------------------------------- | |
*/ | |
/** | |
* \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 ; | |
} | |