CMSIS-Core (Cortex-M)  Version 5.5.0
CMSIS-Core support for Cortex-M processor-based devices
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Startup File startup_<device>.s (deprecated)

The Startup File startup_<device>.s (deprecated) contains:

  • The reset handler which is executed after CPU reset and typically calls the SystemInit function.
  • The setup values for the Main Stack Pointer (MSP).
  • Exception vectors of the Cortex-M Processor with weak functions that implement default routines.
  • Interrupt vectors that are device specific with weak functions that implement default routines.

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

To adapt the file to a new device only the interrupt vector table needs to be extended with the device-specific interrupt handlers. The naming convention for the interrupt handler names are <interrupt_name>_IRQHandler. This table needs to be consistent with IRQn_Type that defines all the IRQ numbers for each interrupt.


The following example shows the extension of the interrupt vector table for the LPC1100 device family.

; External Interrupts
DCD WAKEUP0_IRQHandler ; 16+ 0: Wakeup PIO0.0
DCD WAKEUP1_IRQHandler ; 16+ 1: Wakeup PIO0.1
DCD WAKEUP2_IRQHandler ; 16+ 2: Wakeup PIO0.2
: :
: :
DCD EINT1_IRQHandler ; 16+30: PIO INT1
DCD EINT0_IRQHandler ; 16+31: PIO INT0
: :
: :
B .

startup_Device.S Template File

An Arm Compiler V6 assembler startup_Device.S Template File for an Armv8-M processor like Cortex-M33 is shown below. The files for other compiler vendors differ slightly in the syntax, but not in the overall structure.

 * @file     startup_<Device>.S
 * @brief    CMSIS-Core(M) Device Startup File for
 *           Device <Device> (using Arm Compiler 6 with scatter file)
 * @version  V1.0.0
 * @date     20. January 2021
 * Copyright (c) 2009-2021 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.

                .syntax  unified
/* ToDo: Set .arch to the architecture according the used Cortex-Core */
                .arch    armv8-m.main

                #define __INITIAL_SP     Image$$ARM_LIB_STACK$$ZI$$Limit
                #define __STACK_LIMIT    Image$$ARM_LIB_STACK$$ZI$$Base
                #if defined (__ARM_FEATURE_CMSE) && (__ARM_FEATURE_CMSE == 3U)
                #define __STACK_SEAL     Image$$STACKSEAL$$ZI$$Base

                .section RESET
                .align   2
                .globl   __Vectors
                .globl   __Vectors_End
                .globl   __Vectors_Size
/* ToDo: Add Cortex exception vectors according the used Cortex-Core */
                .long    __INITIAL_SP                       /*     Initial Stack Pointer */
                .long    Reset_Handler                      /*     Reset Handler */
                .long    NMI_Handler                        /* -14 NMI Handler */
                .long    HardFault_Handler                  /* -13 Hard Fault Handler */
                .long    MemManage_Handler                  /* -12 MPU Fault Handler */
                .long    BusFault_Handler                   /* -11 Bus Fault Handler */
                .long    UsageFault_Handler                 /* -10 Usage Fault Handler */
                .long    SecureFault_Handler                /*  -9 Secure Fault Handler */
                .long    0                                  /*     Reserved */
                .long    0                                  /*     Reserved */
                .long    0                                  /*     Reserved */
                .long    SVC_Handler                        /*  -5 SVCall Handler */
                .long    DebugMon_Handler                   /*  -4 Debug Monitor Handler */
                .long    0                                  /*     Reserved */
                .long    PendSV_Handler                     /*  -2 PendSV Handler */
                .long    SysTick_Handler                    /*  -1 SysTick Handler */

/* ToDo: Add your device specific interrupt vectors */
                /* Interrupts */
                .long    <DeviceInterrupt first>_Handler   /*   first Device Interrupt */
                .long    <DeviceInterrupt last>_Handler    /*   last Device Interrupt */

/* ToDo: calculate the empty space according the used Cortex-Core */
                .space   (x * 4)                          /* Interrupts x .. 480 are left out */
                .equ     __Vectors_Size, __Vectors_End - __Vectors
                .size    __Vectors, . - __Vectors

                .section .text
                .align   2

                .type    Reset_Handler, %function
                .globl   Reset_Handler
                ldr      r0, =__INITIAL_SP
                msr      psp, r0

                ldr      r0, =__STACK_LIMIT
                msr      msplim, r0
                msr      psplim, r0

                #if defined (__ARM_FEATURE_CMSE) && (__ARM_FEATURE_CMSE == 3U)
                ldr      r0, =__STACK_SEAL
                ldr      r1, =0xFEF5EDA5U
                strd     r1,r1,[r0,#0]

                bl       SystemInit

                bl       __main

                .size    Reset_Handler, . - Reset_Handler

/* The default macro is not used for HardFault_Handler
 * because this results in a poor debug illusion.
                .type    HardFault_Handler, %function
                .weak    HardFault_Handler
                b        .
                .size    HardFault_Handler, . - HardFault_Handler

                .type    Default_Handler, %function
                .weak    Default_Handler
                b        .
                .size    Default_Handler, . - Default_Handler

/* Macro to define default exception/interrupt handlers.
 * Default handler are weak symbols with an endless loop.
 * They can be overwritten by real handlers.
                .macro   Set_Default_Handler  Handler_Name
                .weak    \Handler_Name
                .set     \Handler_Name, Default_Handler

/* ToDo: Add Cortex exception handler according the used Cortex-Core */
/* Default exception/interrupt handler */
                Set_Default_Handler  NMI_Handler
                Set_Default_Handler  MemManage_Handler
                Set_Default_Handler  BusFault_Handler
                Set_Default_Handler  UsageFault_Handler
                Set_Default_Handler  SecureFault_Handler
                Set_Default_Handler  SVC_Handler
                Set_Default_Handler  DebugMon_Handler
                Set_Default_Handler  PendSV_Handler
                Set_Default_Handler  SysTick_Handler

/* ToDo: Add your device specific interrupt handler */
                Set_Default_Handler  <DeviceInterrupt first>_Handler
                Set_Default_Handler  <DeviceInterrupt last>_Handler