KR-51 Real Time Operating System (RTOS) is designed to provide a variety of operating system functions for applications running on resource constrained 8051 microcontrollers.

The RTOS is implemented as a task scheduling program and service functions that can be called by tasks to send a variety requests to the scheduler. Services include providing time and memory management, semaphores, event synchronization, inter-task communications, plus more sophisticated functions such as a perpetual calendar.

KR-51 is fully integrated into RKit-51 allowing task declaration at the C-source or Assembly source level, and configuration of the kernel at the project level.

Integration with the SIMICE-51 simulator makes it possible to view the status of the Kernel and each task.

A 3 task-limited version of the KR-51 RTOS is available as part of the free RKit51 Toolset. The unlimited KR-51 with up to 125 tasks is available as part of the RKitE51 "Enterprise" version of the tool set.