Arm Cortex-M

Programming

Armv6-M Programming Model

The programming model used in Cortex-M processors with low power consumption. For example, Cortex-M0.

Armv7-M Programming Model

This is the programming model used in Cortex-M processors with higher performance. For example, Cortex-M4.

CMSIS

Arm specifies a standard C interface for programming Cortex-M processors, the Cortex-M Standard Interface (CMSIS). The Arm licensees are strongly encouraged to provide the CMSIS functions as part of their microcontroller programming SDK. Third-party software libraries usually rely on CMSIS availability.

Intrinsic Functions

Functions that generate instructions not provided by ISO/IEC C

Instruction	CMSIS intrinsic function
CPSIE I	void __enable_irq(void)
CPSID I	void __disable_irq(void)
ISB	void __ISB(void)
DSB	void __DSB(void)
DMB	void __DMB(void)
NOP	void __NOP(void)
REV	uint32_t __REV(uint32_t int value)
REV16	uint32_t __REV16(uint32_t int value)
REVSH	uint32_t __REVSH(uint32_t int value)
SEV	void __SEV(void)
WFE	void __WFE(void)
WFI	void __WFI(void)

Functions for accessing special registers

Register	CMSIS read function	CMSIS write function
PRIMASK	uint32_t __get_PRIMASK (void)	void __set_PRIMASK (uint32_t value)
CONTROL	uint32_t __get_CONTROL (void)	void __set_CONTROL (uint32_t value)
MSP	uint32_t __get_MSP (void)	void __set_MSP (uint32_t TopOfMainStack)
PSP	uint32_t __get_PSP (void)	void __set_PSP (uint32_t TopOfProcStack)

Processor Cores

ARM's family of Cortex-M processors (notably M0, M0+, M3, M4) are designed for use as energy-efficient microcontrollers, where M0+ is the cheapest and most efficient, and M4 is the fastest and most capable (offering DSP functions and a floating point unit).

Reference Manuals

• CMSIS abstraction layer for programming Cortex-M processors

Cortex-M0+

• Arm Cortex-M0+
• Generic User Guide
• ARMv6-M Architecture Reference Manual

Cortex-M4

• Arm Cortex-M4
• Generic User Guide
• ARMv7-M Architecture Reference Manual

Development Boards

• Nucleo boards by STMicroelectronics, with STM32 processors
  • Sold by: DigiKey, Reichelt, Conrad, etc.
• Freedom boards by NXP (after buying Freescale), with Kinetis processors
• LPCXpresso boards by NXP
• ARM related products by Olimex

Software Development Tools

• ARM Mbed framework that provides higher-level C++ API, with downloadable or web-based IDE.
• GNU ARM Embedded Toolchain for Ubuntu
  or the latest toolchain for all Linux distros, macOS, and Windows directly from ARM Ltd.
• GNU MCU Eclipse plugin with good support for STM32
• OpenOCD on-chip debugger
• STM32Cube tools and drivers package for STM32 programming (CMSIS and HAL libraries)
• LPCXpresso IDE and utility programs for programming LPCXpresso boards.

Tutorials

• Arm Cortex-M Assembly programming
• Programming the STM Nucleo-64 boards
• Programming the STM Nucleo-32 boards
• Programming the Cortex-M4 development board SAM E54 Xplained Pro
• ARM Bootloader
• ARM GCC Inline Assembler Cookbook by Harald Kipp
• Collection of Cortex-M tutorials by Keil
• Programming STM32F103RET Cortex-M3 with GNU ARM Eclipse Plugin