| CMSIS-Core (Cortex-A) CMSIS-Core support for Cortex-A processor-based devices |

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Startup File startup_<Device>.c

The Startup File startup_<Device>.c contains:

- Exception vectors of the Cortex-A Processor with weak functions that implement default routines.
- The reset handler which is executed after CPU reset and typically calls the SystemInit function.
- The setup values for the various stack pointers, i.e. per exceptional mode and main stack.

The file exists for each supported toolchain and is the only tool-chain specific CMSIS file.

# startup_Device.c Template File

An Arm Compiler specific startup file for an Armv7-A processor like Cortex-A9 is shown below. The files for other compiler vendors differ slightly in the syntax, but not in the overall structure.

    /******************************************************************************
     * @file     startup_<Device>.c
     * @brief    CMSIS Cortex-A Device Startup
     * @version  V1.00
     * @date     10. January 2018
     ******************************************************************************/
    /*
     * Copyright (c) 2009-2018 Arm Limited. All rights reserved.
     *
     * SPDX-License-Identifier: Apache-2.0
     *
     * Licensed under the Apache License, Version 2.0 (the License); you may
     * not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     * www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an AS IS BASIS, WITHOUT
     * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    #include "<Device>.h" /* ToDo: replace '<Device>' with your device name */

    /*----------------------------------------------------------------------------
      Definitions
     *----------------------------------------------------------------------------*/
    #define USR_MODE 0x10            // User mode
    #define FIQ_MODE 0x11            // Fast Interrupt Request mode
    #define IRQ_MODE 0x12            // Interrupt Request mode
    #define SVC_MODE 0x13            // Supervisor mode
    #define ABT_MODE 0x17            // Abort mode
    #define UND_MODE 0x1B            // Undefined Instruction mode
    #define SYS_MODE 0x1F            // System mode

    /*----------------------------------------------------------------------------
      Internal References
     *----------------------------------------------------------------------------*/
    void Vectors       (void) __attribute__ ((section("RESET")));
    void Reset_Handler (void);

    /*----------------------------------------------------------------------------
      Exception / Interrupt Handler
     *----------------------------------------------------------------------------*/
    void Undef_Handler (void) __attribute__ ((weak, alias("Default_Handler")));
    void SVC_Handler   (void) __attribute__ ((weak, alias("Default_Handler")));
    void PAbt_Handler  (void) __attribute__ ((weak, alias("Default_Handler")));
    void DAbt_Handler  (void) __attribute__ ((weak, alias("Default_Handler")));
    void IRQ_Handler   (void) __attribute__ ((weak, alias("Default_Handler")));
    void FIQ_Handler   (void) __attribute__ ((weak, alias("Default_Handler")));

    /*----------------------------------------------------------------------------
      Exception / Interrupt Vector Table
     *----------------------------------------------------------------------------*/
    __ASM void Vectors(void) {
      IMPORT Undef_Handler
      IMPORT SVC_Handler
      IMPORT PAbt_Handler
      IMPORT DAbt_Handler
      IMPORT IRQ_Handler
      IMPORT FIQ_Handler
      LDR    PC, =Reset_Handler
      LDR    PC, =Undef_Handler
      LDR    PC, =SVC_Handler
      LDR    PC, =PAbt_Handler
      LDR    PC, =DAbt_Handler
      NOP
      LDR    PC, =IRQ_Handler
      LDR    PC, =FIQ_Handler
    }

    /*----------------------------------------------------------------------------
      Reset Handler called on controller reset
     *----------------------------------------------------------------------------*/
    __ASM void Reset_Handler(void) {

      // Mask interrupts
      CPSID   if

      // Put any cores other than 0 to sleep
      MRC     p15, 0, R0, c0, c0, 5       // Read MPIDR
      ANDS    R0, R0, #3
    goToSleep
      WFINE
      BNE     goToSleep

      // Reset SCTLR Settings
      MRC     p15, 0, R0, c1, c0, 0       // Read CP15 System Control register
      BIC     R0, R0, #(0x1 << 12)        // Clear I bit 12 to disable I Cache
      BIC     R0, R0, #(0x1 <<  2)        // Clear C bit  2 to disable D Cache
      BIC     R0, R0, #0x1                // Clear M bit  0 to disable MMU
      BIC     R0, R0, #(0x1 << 11)        // Clear Z bit 11 to disable branch prediction
      BIC     R0, R0, #(0x1 << 13)        // Clear V bit 13 to disable hivecs
      MCR     p15, 0, R0, c1, c0, 0       // Write value back to CP15 System Control register
      ISB

      // Configure ACTLR
      MRC     p15, 0, r0, c1, c0, 1       // Read CP15 Auxiliary Control Register
      ORR     r0, r0, #(1 <<  1)          // Enable L2 prefetch hint (UNK/WI since r4p1)
      MCR     p15, 0, r0, c1, c0, 1       // Write CP15 Auxiliary Control Register

      // Set Vector Base Address Register (VBAR) to point to this application's vector table
      LDR    R0, =Vectors
      MCR    p15, 0, R0, c12, c0, 0

      // Setup Stack for each exceptional mode
      IMPORT |Image$$FIQ_STACK$$ZI$$Limit|
      IMPORT |Image$$IRQ_STACK$$ZI$$Limit|
      IMPORT |Image$$SVC_STACK$$ZI$$Limit|
      IMPORT |Image$$ABT_STACK$$ZI$$Limit|
      IMPORT |Image$$UND_STACK$$ZI$$Limit|
      IMPORT |Image$$ARM_LIB_STACK$$ZI$$Limit|
      CPS    #0x11
      LDR    SP, =|Image$$FIQ_STACK$$ZI$$Limit|
      CPS    #0x12
      LDR    SP, =|Image$$IRQ_STACK$$ZI$$Limit|
      CPS    #0x13
      LDR    SP, =|Image$$SVC_STACK$$ZI$$Limit|
      CPS    #0x17
      LDR    SP, =|Image$$ABT_STACK$$ZI$$Limit|
      CPS    #0x1B
      LDR    SP, =|Image$$UND_STACK$$ZI$$Limit|
      CPS    #0x1F
      LDR    SP, =|Image$$ARM_LIB_STACK$$ZI$$Limit|

      // Call SystemInit
      IMPORT SystemInit
      BL     SystemInit

      // Unmask interrupts
      CPSIE  if

      // Call __main
      IMPORT __main
      BL     __main
    }

    /*----------------------------------------------------------------------------
      Default Handler for Exceptions / Interrupts
     *----------------------------------------------------------------------------*/
    void Default_Handler(void) {
      while(1);
    }