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133 lines
4.1 KiB
C
133 lines
4.1 KiB
C
/* ----------------------------------------------------------------------------
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* ATMEL Microcontroller Software Support
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* ----------------------------------------------------------------------------
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* Copyright (c) 2009, Atmel Corporation
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* - Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the disclaimer below.
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*
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* Atmel's name may not be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
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* DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* ----------------------------------------------------------------------------
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*/
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/** \addtogroup rtt_module Working with RTT
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* The RTT driver provides the interface to configure and use the RTT
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* peripheral.
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*
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* The Real-time Timer is used to count elapsed seconds.\n
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* This timer is clocked by the 32kHz system clock divided by a programmable
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* 16-bit balue. To be accurate, it is better to use an
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* external 32kHz crystal instead of the internal 32kHz RC.\n
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*
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* To count elapsed seconds, the user could follow these few steps:
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* <ul>
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* <li>Programming PTPRES in RTT_MR to feeding the timer with a 1Hz signal.</li>
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* <li>Writing the bit RTTRST in RTT_MR to restart the timer with new settings.</li>
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* </ul>
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*
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* An alarm can be set to happen on second by setting alarm value in RTT_AR.
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* Alarm occurence can be detected by polling or interrupt.
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*
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* For more accurate information, please look at the RTT section of the
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* Datasheet.
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*
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* Related files :\n
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* \ref rtt.c\n
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* \ref rtt.h.\n
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*/
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/*@{*/
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/*@}*/
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/**
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* \file
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*
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* Implementation of Real Time Timer (RTT) controller.
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*
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*/
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/*----------------------------------------------------------------------------
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* Headers
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*----------------------------------------------------------------------------*/
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#include "chip.h"
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#include <assert.h>
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/*----------------------------------------------------------------------------
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* Exported functions
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*----------------------------------------------------------------------------*/
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/**
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* \brief Changes the prescaler value of the given RTT and restarts it.
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*
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* \note This function disables RTT interrupt sources.
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*
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* \param rtt Pointer to a Rtt instance.
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* \param prescaler Prescaler value for the RTT.
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*/
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void RTT_SetPrescaler(Rtt *rtt, uint16_t prescaler)
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{
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rtt->RTT_MR = (prescaler | RTT_MR_RTTRST);
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}
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/**
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* \brief Returns the current value of the RTT timer value.
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*
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* \param rtt Pointer to a Rtt instance.
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*/
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uint32_t RTT_GetTime(Rtt *rtt)
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{
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return rtt->RTT_VR;
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}
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/**
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* \brief Enables the specified RTT interrupt sources.
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*
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* \param rtt Pointer to a Rtt instance.
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* \param sources Bitmask of interrupts to enable.
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*/
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void RTT_EnableIT(Rtt *rtt, uint32_t sources)
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{
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assert( (sources & 0x0004FFFF) == 0 ) ;
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rtt->RTT_MR |= sources;
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}
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/**
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* \brief Returns the status register value of the given RTT.
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*
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* \param rtt Pointer to an Rtt instance.
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*/
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uint32_t RTT_GetStatus(Rtt *rtt)
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{
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return rtt->RTT_SR;
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}
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/**
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* \brief Configures the RTT to generate an alarm at the given time.
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*
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* \param pRtt Pointer to an Rtt instance.
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* \param time Alarm time.
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*/
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void RTT_SetAlarm(Rtt *pRtt, uint32_t time)
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{
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assert(time > 0);
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pRtt->RTT_AR = time - 1;
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}
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