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/** \addtogroup tc_module
* The TC driver provides the Interface to configure the Timer Counter (TC).
*
* \section Usage
* <ul>
* <li> Optionally, use TC_FindMckDivisor() to let the program find the best
* TCCLKS field value automatically.</li>
* <li> Configure a Timer Counter in the desired mode using TC_Configure().</li>
* <li> Start or stop the timer clock using TC_Start() and TC_Stop().</li>
*
* </ul>
* For more accurate information, please look at the TC section of the Datasheet.
*
* Related files :\n
* \ref tc.c\n
* \ref tc.h.\n
*/
/**
* \file
*
* \section Purpose
*
* Interface for configuring and using Timer Counter (TC) peripherals.
*
* \section Usage
* -# Optionally, use TC_FindMckDivisor() to let the program find the best
* TCCLKS field value automatically.
* -# Configure a Timer Counter in the desired mode using TC_Configure().
* -# Start or stop the timer clock using TC_Start() and TC_Stop().
*/
/**
* \file
*
* Implementation of Timer Counter (TC).
*
*/
/*------------------------------------------------------------------------------
* Headers
*-----------------------------------------------------------------------------*/
#ifndef __rtems__
#include "board.h"
#else /* __rtems__ */
#include <chip.h>
#endif /* __rtems__ */
#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)
{
/*
TCCLKS:
0 - PCK6: default source - Slow Clock; update according to actual case
4 - SLCK: (slow clock) is either "Embedded 32kHz RC Oscillator" or
"32768Hz Crystal Oscillator"
*/
const uint32_t adwDivisors[5] = { BOARD_MCK / 32768, 8, 32, 128, BOARD_MCK / 32768 };
uint32_t dwIndex = 0;
dwBoardMCK = dwBoardMCK;
/* 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;
}
