# Device support
## In this learning path
- [Introduction](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/pack-migration-cmsis-v6/)
- [Device support](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/pack-migration-cmsis-v6/device_support/)
- [Example projects](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/pack-migration-cmsis-v6/example_projects/)
- [Next Steps](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/pack-migration-cmsis-v6/_next-steps/)
## Supported toolchains
CMSIS v6 supports the following toolchains:
- [Arm Compiler for Embedded (v6 and above)](https://developer.arm.com/Tools%20and%20Software/Arm%20Compiler%20for%20Embedded)
- [Arm GNU Toolchain (v12 and above)](https://developer.arm.com/Tools%20and%20Software/GNU%20Toolchain)
- [LLVM Toolchain (v16 and above)](https://developer.arm.com/Tools%20and%20Software/LLVM%20Toolchain)
- [IAR Embedded Workbench for Arm (v9.30 and above)](https://www.iar.com/ewarm)
Before migrating your project, please make sure that you use one of these toolchains. In this learning path, you will use the Arm Compiler for Embedded v6 toolchain.
## Update the device support
To update the device support, you will need to follow the steps outlined below:
- Switch from assembly based code to [C-based startup files](#create-c-based-startup-code).
- [Create scatter files](#scatter-file-creation) to [place the stack and heap](https://developer.arm.com/documentation/101754/latest/armlink-Reference/Scatter-loading-Features/The-scatter-loading-mechanism/Placing-the-stack-and-heap-with-a-scatter-file).
- [Update the pack](#cmsis-pack-update) with the new contents.
### Create C-based startup code
In CMSIS v6, assembly-based startup code is deprecated. You must move your `startup_device.s` files to `startup_device.c`. This section explains the necessary steps.
1. Copy the `startup_ARMCMx.c` file from the [CMSIS-DFP repo](https://github.com/ARM-software/CMSIS-DFP) into your device support repo. In this example, a Cortex-M4-based device is used (and therefore, the [startup_ARMCM4.c](https://github.com/ARM-software/CMSIS-DFP/blob/main/Device/ARMCM4/Source/startup_ARMCM4.c) is taken from CMSIS-DFP/Device/ARMCM4/source).
2. Copy all the interrupt handler names and wrap them into `void handler_name (void) __attribute__ ((weak, alias("Default_Handler")));`. Place them around line 58 of the template file.
**Code Example**
```assembly
; Interrupt Handlers for Service Requests (SR) from Peripherals */
Entry SCU_0_IRQHandler ; Handler name for SR SCU_0
Entry ERU0_0_IRQHandler ; Handler name for SR ERU0_0
Entry ERU0_1_IRQHandler ; Handler name for SR ERU0_1
Entry ERU0_2_IRQHandler ; Handler name for SR ERU0_2
Entry ERU0_3_IRQHandler ; Handler name for SR ERU0_3
Entry ERU1_0_IRQHandler ; Handler name for SR ERU1_0
Entry ERU1_1_IRQHandler ; Handler name for SR ERU1_1
Entry ERU1_2_IRQHandler ; Handler name for SR ERU1_2
Entry ERU1_3_IRQHandler ; Handler name for SR ERU1_3
DCD 0 ; Not Available
DCD 0 ; Not Available
DCD 0 ; Not Available
Entry PMU0_0_IRQHandler ; Handler name for SR PMU0_0
DCD 0 ; Not Available
Entry VADC0_C0_0_IRQHandler ; Handler name for SR VADC0_C0_0
Entry VADC0_C0_1_IRQHandler ; Handler name for SR VADC0_C0_1
Entry VADC0_C0_2_IRQHandler ; Handler name for SR VADC0_C0_1
Entry VADC0_C0_3_IRQHandler ; Handler name for SR VADC0_C0_3
```
Translates to:
```c
void SCU_0_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU0_0_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU0_1_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU0_2_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU0_3_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU1_0_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU1_1_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU1_2_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void ERU1_3_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void PMU0_0_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void VADC0_C0_0_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void VADC0_C0_1_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void VADC0_C0_2_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
void VADC0_C0_3_IRQHandler (void) __attribute__ ((weak, alias("Default_Handler")));
```
3. Copy the list of names with the empty handlers to the `__VECTOR_TABLE_ATTRIBUTE` separated by commas (around line 99 in the template). Starting from the same assembly exception list as in the previous point, this translates to:
```c
extern const VECTOR_TABLE_Type __VECTOR_TABLE[240];
const VECTOR_TABLE_Type __VECTOR_TABLE[240] __VECTOR_TABLE_ATTRIBUTE = {
(VECTOR_TABLE_Type)(&__INITIAL_SP), /* Initial Stack Pointer */
Reset_Handler, /* Reset Handler */
NMI_Handler, /* -14 NMI Handler */
HardFault_Handler, /* -13 Hard Fault Handler */
MemManage_Handler, /* -12 MPU Fault Handler */
BusFault_Handler, /* -11 Bus Fault Handler */
UsageFault_Handler, /* -10 Usage Fault Handler */
0, /* Reserved */
0, /* Reserved */
0, /* Reserved */
0, /* Reserved */
SVC_Handler, /* -5 SVC Handler */
DebugMon_Handler, /* -4 Debug Monitor Handler */
0, /* Reserved */
PendSV_Handler, /* -2 PendSV Handler */
SysTick_Handler, /* -1 SysTick Handler */
/* Interrupts */
SCU_0_IRQHandler,
ERU0_0_IRQHandler,
ERU0_1_IRQHandler,
ERU0_2_IRQHandler,
ERU0_3_IRQHandler,
ERU1_0_IRQHandler,
ERU1_1_IRQHandler,
ERU1_2_IRQHandler,
ERU1_3_IRQHandler,
0,
0,
0,
PMU0_0_IRQHandler,
0,
VADC0_C0_0_IRQHandler,
VADC0_C0_1_IRQHandler,
VADC0_C0_2_IRQHandler,
VADC0_C0_3_IRQHandler
/* Further interrupts are left out */
};
```
4. Make sure that additional functions (`boot code`, for example) are implemented in C.
5. If you have conditional assembly, replace it with conditional compilation:
**Code Example**
```assembly
IF (USE_CHIP=SOME_CHIP)
DCD WDT_IRQHandler
ELSE
DCD _RESERVED
ENDIF
```
Translates to:
```c
#if (USE_CHIP=SOME_CHIP)
WDT_IRQHandler,
#else
0,
#endif
```
6. Save your new `startup_device.c` file. If you have entries for stack and heap size in the assembly startup file, save these and add them in the next step to the now mandatory scatter file.
### Scatter file creation
1. Copy the scatter file template from the CMSIS-DFP repo into your device support repo. The scatter file template for the Cortex-M4 is called [ARMCM4_ac6.sct](https://github.com/ARM-software/Cortex_DFP/blob/main/Device/ARMCM4/Config/ARMCM4_ac6.sct).
2. Edit the template according to your device settings. These values need to be set:
```c
#define __ROM_BASE 0x00000000
#define __ROM_SIZE 0x00080000
#define __RAM_BASE 0x20000000
#define __RAM_SIZE 0x00040000
#define __STACK_SIZE 0x00000200
#define __HEAP_SIZE 0x00000C00
```
### CMSIS-Pack update
1. Make the necessary changes to your PDSC file. Replace the `startup_device.s` file with the new `startup_device.c` file and add the device’s scatter file as follows:
```xml
```
2. Finally, create a new pack with the updated device support so that you can migrate the projects to Arm Compiler 6.