In a system with a real-time operating system (RTOS), it is general to use a task which realizes the concurrence or to use a semaphore which realizes a mutual exclusion. But about 30% of systems do not employ OS. In the systems without RTOSs, it is general to employ the Interrupt Service Routine (ISR) for realizing the concurrence and to use Interrupt Enable/Disable for realizing the mutual exclusion among several ISRs. Unlike the Semaphore RTOS provides, however, if a system uses the Interrupt Enable/Disable, there is a problem that a speed of the system becomes slow. This is because other ISRs which have not relation with the ISR cannot be executed by the Interrupt Disable mechanism. In addition, for real-time systems, a processing related with ISRs of higher priority may be not finished in a given time limit due to the above reason. Using the proposed method that adopts semaphores to achieve exclusive control among ISRs, the real-time multi-processing of ISRs was achieved successfully in the embedded systems without an RTOS. Therefore, in the systems without RTOS, we have proposed and implemented Real-Time Embedded Monitor called REMON. With REMON, the mutual exclusion which influences only concerned ISRs can be realized.