cstartup_sam7.c

基于ADS1.2的AT91SAM7X256芯片的CAN应用代码。

//*----------------------------------------------------------------------------
//*         ATMEL Microcontroller Software Support  -  ROUSSET  -
//*----------------------------------------------------------------------------
//* The software is delivered "AS IS" without warranty or condition of any
//* kind, either express, implied or statutory. This includes without
//* limitation any warranty or condition with respect to merchantability or
//* fitness for any particular purpose, or against the infringements of
//* intellectual property rights of others.
//*----------------------------------------------------------------------------
//* File Name           : Cstartup_SAM7.c
//* Object              : Low level initializations written in C for IAR
//*                       tools
//* Creation            : 12/Jun/04
//*
//*----------------------------------------------------------------------------


// Include the board file description

#include "AT91SAM7X-EK.h"
#include "AT91SAM7X256.h"
#include "lib_AT91SAM7X256.h"
// The following functions must be write in ARM mode this function called directly by exception vector
extern void AT91F_Spurious_handler(void);
extern void AT91F_Default_IRQ_handler(void);
extern void AT91F_Default_FIQ_handler(void);

//*----------------------------------------------------------------------------
//* \fn    AT91F_LowLevelInit
//* \brief This function performs very low level HW initialization
//*        this function can use a Stack, depending the compilation
//*        optimization mode
//*----------------------------------------------------------------------------
void AT91F_LowLevelInit(void)
{
    unsigned char i;
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    // EFC Init
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_MC->MC_FMR = AT91C_MC_FWS_1FWS;      // 1 Wait State necessary to work at 48MHz

    /////////////////////////////////////////////////////////////////////////////////////////////////////
    // Init PMC Step 1. Enable Main Oscillator
    // Main Oscillator startup time is board specific:
    // Main Oscillator Startup Time worst case (3MHz) corresponds to 15ms (0x40 for AT91C_CKGR_OSCOUNT field)
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_PMC->PMC_MOR = (( AT91C_CKGR_OSCOUNT & (0x40 <<8) | AT91C_CKGR_MOSCEN ));
    // Wait Main Oscillator stabilization
    while(!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MOSCS));

    /////////////////////////////////////////////////////////////////////////////////////////////////////
    // Init PMC Step 2.
    // Set PLL to 96MHz (96,109MHz) and UDP Clock to 48MHz
    // PLL Startup time depends on PLL RC filter: worst case is choosen
    // UDP Clock (48,058MHz) is compliant with the Universal Serial Bus Specification (+/- 0.25% for full speed)
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_PMC->PMC_PLLR = AT91C_CKGR_USBDIV_1 | AT91C_CKGR_OUT_0 | AT91C_CKGR_PLLCOUNT |
      (AT91C_CKGR_MUL & (72 << 16)) | (AT91C_CKGR_DIV & 14);
    // Wait for PLL stabilization
    while( !(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_LOCK) );
    // Wait until the master clock is established for the case we already turn on the PLL
    while( !(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY) );

    /////////////////////////////////////////////////////////////////////////////////////////////////////
    // Init PMC Step 3.
    // Selection of Master Clock MCK (equal to Processor Clock PCK) equal to PLL/2 = 48MHz
    // The PMC_MCKR register must not be programmed in a single write operation (see. Product Errata Sheet)
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_PMC->PMC_MCKR = AT91C_PMC_PRES_CLK_2;
    // Wait until the master clock is established
    while( !(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY) );

    AT91C_BASE_PMC->PMC_MCKR |= AT91C_PMC_CSS_PLL_CLK;
    // Wait until the master clock is established
    while( !(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY) );

    /////////////////////////////////////////////////////////////////////////////////////////////////////
    //  Disable Watchdog (write once register)
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_WDTC->WDTC_WDMR = AT91C_WDTC_WDDIS;

    ////////////////////////////////////////////////////////////////////////////////////////////////////
    //  Init AIC: assign corresponding handler for each interrupt source
    /////////////////////////////////////////////////////////////////////////////////////////////////////
    AT91C_BASE_AIC->AIC_SVR[0] = (int) AT91F_Default_FIQ_handler ;
    for (i = 1; i < 31; i++) {
        AT91C_BASE_AIC->AIC_SVR[i] = (int) AT91F_Default_IRQ_handler ;
    }
    AT91C_BASE_AIC->AIC_SPU = (unsigned int) AT91F_Spurious_handler;
    
    //如果您要仿真，这句话要加。
    AT91C_BASE_MC->MC_RCR  =  1;
}