Overview

CMSIS-Core (Cortex-M) implements the basic run-time system for a Cortex-M device and gives the user access to the processor core and the device peripherals. In detail it defines:

• Hardware Abstraction Layer (HAL) for Cortex-M processor registers with standardized definitions for the SysTick, NVIC, System Control Block registers, MPU registers, FPU registers, and core access functions.
• System exception names to interface to system exceptions without having compatibility issues.
• Methods to organize header files that makes it easy to learn new Cortex-M microcontroller products and improve software portability. This includes naming conventions for device-specific interrupts.
• Methods for system initialization to be used by each MCU vendor. For example, the standardized SystemInit() function is essential for configuring the clock system of the device.
• Intrinsic functions used to generate CPU instructions that are not supported by standard C functions.
• A variable to determine the system clock frequency which simplifies the setup the SysTick timer.

The following sections provide details about the CMSIS-Core (Cortex-M):

• Using CMSIS in Embedded Applications describes the project setup and shows a simple program example.
• Using TrustZone® for Armv8-M describes how to use the security extensions available in the Armv8-M architecture.
• CMSIS-Core Device Templates describes the files of the CMSIS-Core (Cortex-M) in detail and explains how to adapt template files provided by Arm to silicon vendor devices.
• MISRA-C Deviations describes the violations to the MISRA standard.
• Reference describe the features and functions of the Device Header File <device.h> in detail.
• Data Structures describe the data structures of the Device Header File <device.h> in detail.

CMSIS-Core (Cortex-M) in ARM::CMSIS Pack

Files relevant to CMSIS-Core (Cortex-M) are present in the following ARM::CMSIS directories:

File/Folder	Content
CMSIS\Documentation\Core	This documentation
CMSIS\Core\Include	CMSIS-Core (Cortex-M) header files (for example core_cm3.h, core_cmInstr.h, etc.)
Device	Arm reference implementations of Cortex-M devices
Device\_Template_Vendor	CMSIS-Core Device Templates for extension by silicon vendors

Processor Support

CMSIS supports the complete range of Cortex-M processors and the Armv8-M/v8.1-M architecture including security extensions.

Cortex-M Generic User Guides

The Cortex-M Device Generic User Guides contain the programmers model and detailed information about the core peripherals and are available for:

• Cortex-M0 Devices Generic User Guide (Armv6-M architecture)
• Cortex-M0+ Devices Generic User Guide (Armv6-M architecture)
• Cortex-M3 Devices Generic User Guide (Armv7-M architecture)
• Cortex-M4 Devices Generic User Guide (Armv7-M architecture)
• Cortex-M7 Devices Generic User Guide (Armv7-M architecture)
• Cortex-M23 Devices Generic User Guide (Armv8-M architecture)
• Cortex-M33 Devices Generic User Guide (Armv8-M architecture)
• Cortex-M55 Devices Generic User Guide (Armv8.1-M architecture)
• Cortex-M85 Devices Generic User Guide (Armv8.1-M architecture)

CMSIS also supports the following Cortex-M processor variants:

• Cortex-M1 is a processor designed specifically for implementation in FPGAs (Armv6-M architecture).
• SecurCore SC000 is designed specifically for smartcard and security applications (Armv6-M architecture).
• SecurCore SC300 is designed specifically for smartcard and security applications (Armv7-M architecture).
• Cortex-M35P is a tamper resistant Cortex-M processor with optional software isolation using TrustZone for Armv8-M.
• STAR-MC1 is a variant of Armv8-M with TrustZone designed by Arm China.

Armv8-M and Armv8.1-M Architecture

Armv8-M introduces two profiles baseline (for power and area constrained applications) and mainline (full-featured with optional SIMD, floating-point, and co-processor extensions). Both Armv8-M profiles and Armv8.1-M are supported by CMSIS.

The Armv8-M architecture is described in the Armv8-M Architecture Reference Manual.

The Armv8.1-M architecture further extends Armv8-M with Helium (the so called M-Profile Vector Extension (MVE)), as well as further instruction set and debug extensions. More information about Armv8.1-M architecture is available under Arm Helium technology.

Tested and Verified Toolchains

The CMSIS-Core Device Templates supplied by Arm have been tested and verified with the following toolchains:

• Arm: Arm Compiler 5.06 update 7 (not for Cortex-M23/33/35P/55/85, Armv8-M, Armv8.1-M)
• Arm: Arm Compiler 6.16
• Arm: Arm Compiler 6.6.4 (not for Cortex-M0/23/33/35P/55/85, Armv8-M, Armv8.1-M)
• GNU: GNU Arm Embedded Toolchain 10-2020-q4-major (10.2.1 20201103)
• IAR: IAR ANSI C/C++ Compiler for Arm 8.20.1.14183