Two types of RTOS are available for the 8051 family:
- KR-51Tiny which is a 'lite' version of the Kernel and supports either 3 or 8 tasks depending on the software kit.
- KR-51 which is the full version with up to 125 tasks.

KR-51Tiny

KR-51Tiny is an RTOS for the 8051 family and offers a variety of services, providing time and memory management, semaphores, synchronizing events, inter-task communications, and more sophisticated functions such as a perpetual calendar.
KR-51Tiny is limited in the number of tasks according to the software used:
- EVAL51 (demonstration version): 3 tasks
- Lite Suite RKitL51: 8 tasks
- Professional Kit RKitP51: 8 tasks.

Task declaration is done at the 'C'-source level, while configuration of the kernel is made at the project level. The SIMICE-51 simulator provides a variety of information on the status of the Kernel and each task.

The KR-51Tiny executive is a real-time kernel for the 8051 microcontroller family. Placed at the core of an application, it provides efficient task scheduling by driving :

• task activation : initiate, waiting or stop.

• task relationships.

KR-51Tiny is easy to implement and permits the programmer to concentrate on each task, independently from the remaining application. KR-51Tiny recognizes tasks written in either assembly or 'C', (MA-51 and RC-51 respectively).

KR-51 consists of two parts :

• the scheduler which is the task scheduling program.

• the services or functions that can be called by tasks to send various requests to the scheduler.

Full KR-51

KR-51 is fully integrated in the Enterprise Kit RKitE51 version of the software. It has the same features as KR-51Tiny but with up to 125 tasks instead of just 3 or 8.