Christina Quast | 8be71e4 | 2014-12-02 13:06:01 +0100 | [diff] [blame] | 1 | /* ----------------------------------------------------------------------------
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| 2 | * ATMEL Microcontroller Software Support
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| 3 | * ----------------------------------------------------------------------------
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| 4 | * Copyright (c) 2009, Atmel Corporation
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| 5 | *
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| 6 | * All rights reserved.
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| 7 | *
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| 8 | * Redistribution and use in source and binary forms, with or without
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| 9 | * modification, are permitted provided that the following conditions are met:
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| 10 | *
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| 11 | * - Redistributions of source code must retain the above copyright notice,
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| 12 | * this list of conditions and the disclaimer below.
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| 13 | *
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| 14 | * Atmel's name may not be used to endorse or promote products derived from
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| 15 | * this software without specific prior written permission.
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| 16 | *
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| 17 | * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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| 19 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
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| 20 | * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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| 22 | * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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| 23 | * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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| 24 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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| 25 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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| 26 | * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | * ----------------------------------------------------------------------------
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| 28 | */
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| 29 |
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| 30 | /**
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| 31 | * \file
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| 32 | *
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| 33 | * Implementation of Timer Counter (TC).
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| 34 | *
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| 35 | */
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| 36 |
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| 37 | /*------------------------------------------------------------------------------
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| 38 | * Headers
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| 39 | *------------------------------------------------------------------------------*/
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| 40 |
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| 41 | #include "chip.h"
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| 42 |
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| 43 | #include <assert.h>
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| 44 |
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| 45 | /*------------------------------------------------------------------------------
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| 46 | * Global functions
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| 47 | *------------------------------------------------------------------------------*/
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| 48 |
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| 49 | /**
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| 50 | * \brief Configures a Timer Counter Channel
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| 51 | *
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| 52 | * Configures a Timer Counter to operate in the given mode. Timer is stopped
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| 53 | * after configuration and must be restarted with TC_Start(). All the
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| 54 | * interrupts of the timer are also disabled.
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| 55 | *
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| 56 | * \param pTc Pointer to a Tc instance.
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| 57 | * \param channel Channel number.
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| 58 | * \param mode Operating mode (TC_CMR value).
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| 59 | */
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| 60 | extern void TC_Configure( Tc *pTc, uint32_t dwChannel, uint32_t dwMode )
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| 61 | {
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| 62 | TcChannel* pTcCh ;
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| 63 |
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| 64 | assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
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| 65 | pTcCh = pTc->TC_CHANNEL+dwChannel ;
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| 66 |
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| 67 | /* Disable TC clock */
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| 68 | pTcCh->TC_CCR = TC_CCR_CLKDIS ;
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| 69 |
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| 70 | /* Disable interrupts */
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| 71 | pTcCh->TC_IDR = 0xFFFFFFFF ;
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| 72 |
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| 73 | /* Clear status register */
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| 74 | pTcCh->TC_SR ;
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| 75 |
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| 76 | /* Set mode */
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| 77 | pTcCh->TC_CMR = dwMode ;
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| 78 | }
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| 79 |
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| 80 | /**
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| 81 | * \brief Reset and Start the TC Channel
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| 82 | *
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| 83 | * Enables the timer clock and performs a software reset to start the counting.
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| 84 | *
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| 85 | * \param pTc Pointer to a Tc instance.
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| 86 | * \param dwChannel Channel number.
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| 87 | */
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| 88 | extern void TC_Start( Tc *pTc, uint32_t dwChannel )
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| 89 | {
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| 90 | TcChannel* pTcCh ;
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| 91 |
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| 92 | assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
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| 93 |
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| 94 | pTcCh = pTc->TC_CHANNEL+dwChannel ;
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| 95 | pTcCh->TC_CCR = TC_CCR_CLKEN | TC_CCR_SWTRG ;
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| 96 | }
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| 97 |
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| 98 | /**
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| 99 | * \brief Stop TC Channel
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| 100 | *
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| 101 | * Disables the timer clock, stopping the counting.
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| 102 | *
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| 103 | * \param pTc Pointer to a Tc instance.
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| 104 | * \param dwChannel Channel number.
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| 105 | */
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| 106 | extern void TC_Stop(Tc *pTc, uint32_t dwChannel )
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| 107 | {
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| 108 | TcChannel* pTcCh ;
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| 109 |
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| 110 | assert( dwChannel < (sizeof( pTc->TC_CHANNEL )/sizeof( pTc->TC_CHANNEL[0] )) ) ;
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| 111 |
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| 112 | pTcCh = pTc->TC_CHANNEL+dwChannel ;
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| 113 | pTcCh->TC_CCR = TC_CCR_CLKDIS ;
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| 114 | }
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| 115 |
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| 116 | /**
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| 117 | * \brief Find best MCK divisor
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| 118 | *
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| 119 | * Finds the best MCK divisor given the timer frequency and MCK. The result
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| 120 | * is guaranteed to satisfy the following equation:
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| 121 | * \code
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| 122 | * (MCK / (DIV * 65536)) <= freq <= (MCK / DIV)
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| 123 | * \endcode
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| 124 | * with DIV being the highest possible value.
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| 125 | *
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| 126 | * \param dwFreq Desired timer frequency.
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| 127 | * \param dwMCk Master clock frequency.
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| 128 | * \param dwDiv Divisor value.
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| 129 | * \param dwTcClks TCCLKS field value for divisor.
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| 130 | * \param dwBoardMCK Board clock frequency.
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| 131 | *
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| 132 | * \return 1 if a proper divisor has been found, otherwise 0.
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| 133 | */
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| 134 | extern uint32_t TC_FindMckDivisor( uint32_t dwFreq, uint32_t dwMCk, uint32_t *dwDiv, uint32_t *dwTcClks, uint32_t dwBoardMCK )
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| 135 | {
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| 136 | const uint32_t adwDivisors[5] = { 2, 8, 32, 128, dwBoardMCK / 32768 } ;
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| 137 |
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| 138 | uint32_t dwIndex = 0 ;
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| 139 |
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| 140 | /* Satisfy lower bound */
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| 141 | while ( dwFreq < ((dwMCk / adwDivisors[dwIndex]) / 65536) )
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| 142 | {
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| 143 | dwIndex++ ;
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| 144 |
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| 145 | /* If no divisor can be found, return 0 */
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| 146 | if ( dwIndex == (sizeof( adwDivisors )/sizeof( adwDivisors[0] )) )
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| 147 | {
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| 148 | return 0 ;
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| 149 | }
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| 150 | }
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| 151 |
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| 152 | /* Try to maximize DIV while satisfying upper bound */
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| 153 | while ( dwIndex < 4 )
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| 154 | {
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| 155 |
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| 156 | if ( dwFreq > (dwMCk / adwDivisors[dwIndex + 1]) )
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| 157 | {
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| 158 | break ;
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| 159 | }
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| 160 | dwIndex++ ;
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| 161 | }
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| 162 |
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| 163 | /* Store results */
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| 164 | if ( dwDiv )
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| 165 | {
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| 166 | *dwDiv = adwDivisors[dwIndex] ;
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| 167 | }
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| 168 | if ( dwTcClks )
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| 169 | {
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| 170 | *dwTcClks = dwIndex ;
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| 171 | }
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| 172 |
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| 173 | return 1 ;
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| 174 | }
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| 175 |
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