firmware/atmel_softpack_libraries/libchip_sam3s/source/crccu.c

/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support
 * ----------------------------------------------------------------------------
 * Copyright (c) 2009, Atmel Corporation
 *
 * All rights reserved.
 *
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 * modification, are permitted provided that the following conditions are met:
 *
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 * this list of conditions and the disclaimer below.
 *
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 * this software without specific prior written permission.
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/** \addtogroup crccu_module Working with CRCCU
 * The CRCCU driver provides the interface to configure and use the CRCCU
 * peripheral.
 *
 * It performs a CRC computation on a Memory Area. CRC computation is performed
 * from the LSB to MSB bit. Three different polynomials are available:
 * CCIT802.3, CASTAGNOLI and CCIT16.
 *
 * To computes CRC of a buffer, the user has to follow these few steps:
 * <ul>
 * <li>Reset initial CRC by setting RESET bit in CRCCU_CRC_CR,</li>
 * <li>Configure CRC descriptor and working mode,</li>
 * <li>Start to compute CRC by setting DMAEN in CRCCU_DMA_EN,</li>
 * <li>Get CRC value in CRCCU_CRC_SR.</li>
 * </ul>
 *
 * For more accurate information, please look at the CRCCU section of the
 * Datasheet.
 *
 * Related files :\n
 * \ref crccu.c\n
 * \ref crccu.h.\n
*/
/*@{*/
/*@}*/

/**
 * \file
 *
 * Implementation of Cyclic Redundancy Check Calculation Unit (CRCCU).
 *
 */

/*----------------------------------------------------------------------------
 *        Headers
 *----------------------------------------------------------------------------*/
#include "chip.h"

/*----------------------------------------------------------------------------
 *        Definitions
 *----------------------------------------------------------------------------*/
#define CRCCU_TIMEOUT    0xFFFFFFFF

/*----------------------------------------------------------------------------
 *        Exported functions
 *----------------------------------------------------------------------------*/
/**
 * \brief Reset initial CRC to 0xFFFFFFFF.
 */
extern void CRCCU_ResetCrcValue( Crccu* pCrccu )
{
    pCrccu->CRCCU_CR = CRCCU_CR_RESET;
}

/**
 * \brief Configure the CRCCU.
 *
 * \param dscrAddr CRC decscriptor address.
 * \param mode     CRC work mode
 */
extern void CRCCU_Configure( Crccu* pCrccu, uint32_t dwDscrAddr, uint32_t dwMode )
{
    pCrccu->CRCCU_DSCR = dwDscrAddr ;
    pCrccu->CRCCU_MR = dwMode ;
}

/**
 * \brief Start to compute the CRC of a buffer.
 *
 * \return The CRC of the buffer.
 */
extern uint32_t CRCCU_ComputeCrc( Crccu* pCrccu )
{
    uint32_t dwTimeout = 0 ;

    pCrccu->CRCCU_DMA_EN = CRCCU_DMA_EN_DMAEN ;

    while ( ((pCrccu->CRCCU_DMA_SR & CRCCU_DMA_SR_DMASR) == CRCCU_DMA_SR_DMASR) &&
            (dwTimeout++ < CRCCU_TIMEOUT) ) ;

    return (pCrccu->CRCCU_SR) ;
}