+

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);
+}
+