CMSIS-Core (Cortex-A)  Version 1.2.1
CMSIS-Core support for Cortex-A processor-based devices
 All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
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
 * 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 */

#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
  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
  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

  // 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) {