The Common Microcontroller Software Interface Standard (CMSIS) simplifies microcontroller software development, providing a consistent and efficient interface for developers working with Cortex-M and entry-level Cortex-A processors. It promotes code reuse, portability, and interoperability, enabling developers to focus on application-level logic rather than dealing with low-level hardware details.

CMSIS provides interfaces to processor and peripherals, real-time operating systems, and middleware components and includes a delivery mechanism (CMSIS-Pack) for devices, boards, and software, and enables the combination of software components from multiple vendors. The content on keil.arm.com is extracted directly from CMSIS-Packs.

CMSIS is defined in close cooperation with various silicon and software vendors and provides a common approach to interface to peripherals, real-time operating systems, and middleware components. It is intended to enable interoperability of software components from multiple vendors.