Bailey Infi90 Interface to the pi system
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| Principles of Operation 14 disestablish point define nodes get system time set system time connect points read exceptions read miscellaneous status exceptions output value group output value (CIU02 only reread read data exceptions (CIU04 only output report (CIU04 only) Failover The user may run two copies of the interface in a failover configuration whereby one copy fails over to another. These two copies are designated as either the Primary or the Secondary. Initially, the Primary is responsible for data collection while the Secondary runs in standby mode. The Primary and Secondary communicate indirectly with each other via a watchdog signal on the Net. Specifically, the Primary periodically writes watchdog messages. When the Secondary interface times out in receiving these watchdog messages, it takes over data collection. When the Primary interface comes back online (i.e., starts writing watchdog messages, the Secondary interface stops data collection and drop back to waiting mode. The failover scheme covers the cases of Windows computer failure, CIU communication failure, CIU failure, and interface program crashes. Note that there is a limitation on this failover scheme. The limitation applies to PI to Net points (i.e., output points. The primary and the secondary CIU must to have different PCU addresses because it is possible that they are both online at the same time (when the primary Windows computer fails, the primary CIU is still online. Hence, the failover is only seamless for input to PI. However, when the Secondary interface is active, the outputs from PI have different N addresses. Accordingly, any PCU configuration reading from the CIU must be able to switch to the secondary CIU when the primary CIU watchdog stops updating. So, for output points, the user needs to modify the existing PCU configuration to take advantage of the failover. There are three startup command parameters related to failover. The startup command parameter –failover indicates whether a copy of the Interface is running in a failover configuration a value of 0 indicates no failover; 1 indicates that the interface is running as the Primary and 2 indicates that the interface is running as the Secondary. When the command parameter Download 0.78 Mb. Share with your friends:
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