Design of deterministic OS for SPLC

Existing safety PLCs for using in nuclear power plants operates based on priority based scheduling, in which the highest priority task runs first. This type of scheduling scheme determines processing priorities when multiple requests for processing or when there is a lack of resources available for processing, guaranteeing execution of higher priority tasks. This type of scheduling is prone to exhaustion of resources and continuous preemptions by devices with high priorities, and therefore there is uncertainty every period in terms of smooth running of the overall system. Hence, it is difficult to apply this type of scheme to where deterministic operation is required, such as in nuclear power plant. Also, existing PLCs either have no output logic with regard to devices' redundant selection or it was set in a fixed way, and as a result it was extremely inefficient to use them for redundant systems such as that of a nuclear power plant and their use was limited. Therefore, functional modules that can manage and control all devices need to be developed by improving on the way priorities are assigned among the devices, making it more flexible. A management module should be able to schedule all devices of the system, manage resources, analyze states of the devices, and give warnings in case of abnormal situations, such as device fail or resource scarcity and decide on how to handle it. Also, the management module should have output logic for device redundancy, as well as deterministic processing capabilities, such as with regard to device interrupt events