This paper presents a Real-Time Operating System ( RTOS) implementation. This RTOS is based on the OSEK-OS 2.2.3 standard, which will be extended to support an Asymmetric Multiprocessor System ( AMP). The term asymmetric means that the microprocessors included in the system have heterogeneous architectures ( a subgroup of identical processors may exist but not the whole amount of them are identical) and each processor executes an instance of the RTOS specifically designed and optimised. Also, a description of the development process that took place to communicate each RTOS instance, taking advantage of hardware features in order to exchange information between processors, is provided. Finally, a functional test application is presented: Processors monitor each other using RTOS resources as keep-alive events while sharing information about GPIO activity and reporting changes and system status using serial communication. In addition, an energy consumption analysis is performed for this test case. The hardware platform used in this development is the Argentine Open Industrial Computer ( Computadora Industrial Abierta Argentina, CIAA) based on the LPC4337 dual-core AMP microcontroller, which includes an ARM Cortex-M4 ( ARMv7E-M architecture) acting as the master microprocessor and an ARM Cortex-M0 ( ARMv6-M architecture), as the slave coprocessor.