Keil Logo Arm Logo


This chapter describes the powerful Keil RTX Real-Time Operating System (RTX-RTOS) designed for microcontrollers based on ARM7™TDMI, ARM9™, and Cortex™-M CPU cores. The RTX kernel can be used for creating applications that perform multiple functions or tasks simultaneously.

While it is certainly possible to create real-time applications without an RTOS (by executing one or more tasks in a loop), there are numerous scheduling, maintenance, and timing issues that can be solved better with an RTOS. For example, an RTOS enables flexible scheduling of system resources like CPU and memory, and offers methods to communicate between tasks.

RTX programs are written using standard C constructs and are compiled with the ARM Compiler. The RTL.H header file defines the RTX functions and macros that allow declaring tasks and accessing all RTOS features easily.

This chapter contains the following sections:

Provides an overview about the RL-RTX basic functions, inter-process communication and technical specifications.
Theory of Operation
Describes the resources and their management, such as scheduling, task and stack management, interrupts, and timers.
Configuring RL-RTX
Describes the basic and advanced RTX configuration options, and lists the RL-RTX library files.
Using RL-RTX
Provides instructions for writing and debugging applications.
Function Reference
Describes the RTX functions.

The topic Create New RTX Application provides a step-by-step introduction that explains you how to create RTX applications.

Keil logo

Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.

Change Settings

Privacy Policy Update

ARM’s Privacy Policy has been updated. By continuing to use our site, you consent to ARM’s Privacy Policy. Please review our Privacy Policy to learn more about our collection, use and transfers
of your data.

Acquisition of ARM Holdings plc. by SoftBank Group Corp.

We are pleased to inform you that on 5 September 2016, SoftBank Group Corp. acquired ARM Holdings Plc. ARM will continue to operate as an independent business within the SoftBank group.

Any current agreements between ARM Ltd (or other ARM group companies, as applicable) you / your company remain in effect as between the parties, and the parties will continue to be bound by and perform the obligations in such agreements. If you have any queries please direct these to