| 摘要 |
PROBLEM TO BE SOLVED: To simplify the test of the safety system of a plant. SOLUTION: A cause and effect function block, which can be easily integrated into a function block diagram programming environment in a process plant safety system to implement a cause and effect logic, includes a set of cause inputs and a set of effect outputs. A multiplexer within the cause and effect function block receives each of the cause inputs and is coupled to one or more state machines, with a separate state machine existing for each effect output. The multiplexer decodes each of the cause inputs and, based on the cause inputs and cause and effect matrix logic, provides a trip signal to one or more of the state machines. Upon receiving a trip signal, a state machine forces an associated effect output into a tripped or safe state. If desired, the state machine may then use one or more other signals, such as signals from a user or from the process, to transition between a set of different states used to safely return the process plant back to the normal operating state from the tripped or safe state. COPYRIGHT: (C)2005,JPO&NCIPI
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