board_lowlevel.c

Atmel的AT91SAM7X256的和24系列EEPROM通讯的源程序

/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support  -  SDC  -
 * ----------------------------------------------------------------------------
 * Copyright (c) 2006, Atmel Corporation
 *
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 * this software without specific prior written permission.
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 */

/*!
    Low-level initialization routine for the AT91SAM7SE-EK.
 */

//------------------------------------------------------------------------------
//         Headers
//------------------------------------------------------------------------------

#include "board.h"
#include "board_memories.h"

//------------------------------------------------------------------------------
//         Internal definitions
//------------------------------------------------------------------------------
/*
    Constants: Clock and PLL settings

        BOARD_OSCOUNT - Startup time of main oscillator (in number of slow clock
                        ticks). 
        BOARD_USBDIV - USB PLL divisor value to obtain a 48MHz clock.
        BOARD_CKGR_PLL - PLL frequency range.
        BOARD_PLLCOUNT - PLL startup time (in number of slow clock ticks).
        BOARD_MUL - PLL MUL value.
        BOARD_DIV - PLL DIV value.
        BOARD_PRESCALER - Master clock prescaler value.
*/
#define BOARD_OSCOUNT           (AT91C_CKGR_OSCOUNT & (0x40 << 8))
#define BOARD_USBDIV            AT91C_CKGR_USBDIV_1
#define BOARD_CKGR_PLL          AT91C_CKGR_OUT_0
#define BOARD_PLLCOUNT          (16 << 8)
#define BOARD_MUL               (AT91C_CKGR_MUL & (72 << 16))
#define BOARD_DIV               (AT91C_CKGR_DIV & 14)
#define BOARD_PRESCALER         AT91C_PMC_PRES_CLK_2

//------------------------------------------------------------------------------
//         Internal functions
//------------------------------------------------------------------------------
/*!
    Default spurious interrupt handler
 */
void defaultSpuriousHandler( void )
{
    while (1);
}

/*!
    Default handler for fast interrupt requests.
 */
void defaultFiqHandler( void )
{
    while (1);
}

/*!
    Default handler for standard interrupt requests.
 */
void defaultIrqHandler( void )
{
    while (1);
}

//------------------------------------------------------------------------------
//         Exported functions
//------------------------------------------------------------------------------
/*!
    Performs the low-level initialization of the chip.
 */
void LowLevelInit( void )
{
    unsigned char i;

    /* Set flash wait states in the EFC
     **********************************/
    /* 48MHz = 1 wait state */
#if defined(at91sam7x512)
    AT91C_BASE_EFC0->EFC_FMR = AT91C_MC_FWS_1FWS;
    AT91C_BASE_EFC1->EFC_FMR = AT91C_MC_FWS_1FWS;
#elif defined(at91sam7x128) || defined(at91sam7x256)
    AT91C_BASE_MC->MC_FMR = AT91C_MC_FWS_1FWS;
#else
    #error No chip definition ?
#endif

    /* Initialize main oscillator
     ****************************/
    AT91C_BASE_PMC->PMC_MOR = BOARD_OSCOUNT | AT91C_CKGR_MOSCEN;
    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MOSCS));

    /* Initialize PLL at 96MHz (96.109) and USB clock to 48MHz */
    AT91C_BASE_PMC->PMC_PLLR = BOARD_USBDIV | BOARD_CKGR_PLL | BOARD_PLLCOUNT
                               | BOARD_MUL | BOARD_DIV;
    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_LOCK));

    /* Wait for the master clock if it was already initialized */
    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));

    /* Switch to fast clock
     **********************/
    /* Switch to slow clock + prescaler */
    AT91C_BASE_PMC->PMC_MCKR = BOARD_PRESCALER;
    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));

    /* Switch to fast clock + prescaler */
    AT91C_BASE_PMC->PMC_MCKR |= AT91C_PMC_CSS_PLL_CLK;
    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));

    /* Initialize AIC
     ****************/
    AT91C_BASE_AIC->AIC_IDCR = 0xFFFFFFFF;
    AT91C_BASE_AIC->AIC_SVR[0] = (unsigned int) defaultFiqHandler;
    for (i = 1; i < 31; i++) {

        AT91C_BASE_AIC->AIC_SVR[i] = (unsigned int) defaultIrqHandler;
    }
    AT91C_BASE_AIC->AIC_SPU = (unsigned int) defaultSpuriousHandler;

    // Unstack nested interrupts
    for (i = 0; i < 8 ; i++) {

        AT91C_BASE_AIC->AIC_EOICR = 0;
    }

    // Enable Debug mode
    AT91C_BASE_AIC->AIC_DCR = AT91C_AIC_DCR_PROT;

    /* Watchdog initialization
     *************************/
    AT91C_BASE_WDTC->WDTC_WDMR = AT91C_WDTC_WDDIS;

    /* Remap
     *******/
    BOARD_RemapRam();
}