| 摘要 |
A process control system has a programmable controller (SPS) that in normal operation provides full control of a number of peripheral modules (22,24,26,28), via interfaces (14,16,18,20) coupled to the bus. In the event of a system failure, an emergency control mode is engaged. This uses simulation modules (14.1,16.1,18.1,20.1) that are activated to maintain essential functions. During normal operation the simulation modules are inactive.
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