00001 /* ---------------------------------------------------------------------------- */ 00002 /* Atmel Microcontroller Software Support */ 00003 /* SAM Software Package License */ 00004 /* ---------------------------------------------------------------------------- */ 00005 /* Copyright (c) 2015, Atmel Corporation */ 00006 /* */ 00007 /* All rights reserved. */ 00008 /* */ 00009 /* Redistribution and use in source and binary forms, with or without */ 00010 /* modification, are permitted provided that the following condition is met: */ 00011 /* */ 00012 /* - Redistributions of source code must retain the above copyright notice, */ 00013 /* this list of conditions and the disclaimer below. */ 00014 /* */ 00015 /* Atmel's name may not be used to endorse or promote products derived from */ 00016 /* this software without specific prior written permission. */ 00017 /* */ 00018 /* DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR */ 00019 /* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */ 00020 /* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE */ 00021 /* DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, */ 00022 /* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT */ 00023 /* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, */ 00024 /* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF */ 00025 /* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING */ 00026 /* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */ 00027 /* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ 00028 /* ---------------------------------------------------------------------------- */ 00029 00030 /** \addtogroup rtt_module Working with RTT 00031 * \ingroup peripherals_module 00032 * The RTT driver provides the interface to configure and use the RTT 00033 * peripheral. 00034 * 00035 * The Real-time Timer is used to count elapsed seconds.\n 00036 * This timer is clocked by the 32kHz system clock divided by a programmable 00037 * 16-bit value. To be accurate, it is better to use an 00038 * external 32kHz crystal instead of the internal 32kHz RC.\n 00039 * 00040 * To count elapsed seconds, the user could follow these few steps: 00041 * <ul> 00042 * <li>Programming PTPRES in RTT_MR to feeding the timer with a 1Hz signal.</li> 00043 * <li>Writing the bit RTTRST in RTT_MR to restart the timer with new settings. 00044 * </li> 00045 * </ul> 00046 * 00047 * An alarm can be set to happen on second by setting alarm value in RTT_AR. 00048 * Alarm occurrence can be detected by polling or interrupt. 00049 * 00050 * For more accurate information, please look at the RTT section of the 00051 * Datasheet. 00052 * 00053 * Related files :\n 00054 * \ref rtt.c\n 00055 * \ref rtt.h.\n 00056 */ 00057 /*@{*/ 00058 /*@}*/ 00059 00060 /** 00061 * \file 00062 * 00063 * Implementation of Real Time Timer (RTT) controller. 00064 * 00065 */ 00066 00067 /*---------------------------------------------------------------------------- 00068 * Headers 00069 *----------------------------------------------------------------------------*/ 00070 #include "chip.h" 00071 00072 #include <assert.h> 00073 00074 /*---------------------------------------------------------------------------- 00075 * Exported functions 00076 *----------------------------------------------------------------------------*/ 00077 00078 /** 00079 * \brief Changes the prescaler value of the given RTT and restarts it. 00080 * 00081 * \note This function disables RTT interrupt sources. 00082 * 00083 * \param rtt Pointer to a Rtt instance. 00084 * \param prescaler Prescaler value for the RTT. 00085 */ 00086 void RTT_SetPrescaler(Rtt *rtt, uint16_t prescaler) 00087 { 00088 rtt->RTT_MR = (prescaler | RTT_MR_RTTRST); 00089 } 00090 00091 /** 00092 * \brief Returns the current value of the RTT timer value. 00093 * 00094 * \param rtt Pointer to a Rtt instance. 00095 */ 00096 uint32_t RTT_GetTime(Rtt *rtt) 00097 { 00098 return rtt->RTT_VR; 00099 } 00100 00101 /** 00102 * \brief Enables the specified RTT interrupt sources. 00103 * 00104 * \param rtt Pointer to a Rtt instance. 00105 * \param sources Bitmask of interrupts to enable. 00106 */ 00107 void RTT_EnableIT(Rtt *rtt, uint32_t sources) 00108 { 00109 assert((sources & 0x0004FFFF) == 0); 00110 rtt->RTT_MR |= sources; 00111 } 00112 00113 /** 00114 * \brief Returns the status register value of the given RTT. 00115 * 00116 * \param rtt Pointer to an Rtt instance. 00117 */ 00118 uint32_t RTT_GetStatus(Rtt *rtt) 00119 { 00120 return rtt->RTT_SR; 00121 } 00122 00123 /** 00124 * \brief Configures the RTT to generate an alarm at the given time. 00125 * 00126 * \param pRtt Pointer to an Rtt instance. 00127 * \param time Alarm time. 00128 */ 00129 void RTT_SetAlarm(Rtt *pRtt, uint32_t time) 00130 { 00131 assert(time > 0); 00132 00133 pRtt->RTT_AR = time - 1; 00134 }