Pi interface for Bailey Infi90
/delayseconds or check for PI point database updates. If the timesync parameter /tsync
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- Principles of Operation 8
| /delay seconds or check for PI point database updates. If the timesync parameter /tsync is positive and thirty minutes have passed since the last time synchronization, then do time synchronization. For CIU04s, the algorithm is the similar. The only difference is that reading exceptions and reading miscellaneous status exceptions are combined into a single command. The interface program periodically checks for changes in the PI point database and automatically accounts for the modification, addition, and deletion of points. Thus, there is no need fora program restart if interface points are edited. Each time the interface processes a point change, it writes a message to the PIPC.LOG . Hence, the user can trace the progress on the point database change. However, it may take sometime for the program to pickup all the changes when a large number of tags are changed. Accordingly, if the user has changed a large number of points, it will be faster for the changes to take effect if the user restarts the interface. If the interface program hasten consecutive IO errors, it will try to restart the CIU. All communication errors are recorded in the PIPC.LOG file. Consecutive errors of the same type are redacted in the log file only once. Principles of Operation 8 The CIU commands used by the BaInfi90 interface are Restart CIU Establish point Establish report 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 You can run two copies of the interface in a failover configuration whereby one copy fails over to another. These two copies are designated as the Primary and the Secondary. Initially, the Primary collects data while the Secondary runs in standby mode. The Primary and Secondary communicate indirectly with each other through 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 and starts writing watchdog messages, the Secondary interface stops data collection and returns 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-Net90 points, that is, 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, you need to modify the existing PCU configuration to take advantage of the failover. |