Are FieldPoint Read and Write Synchronous Functions?Hardware: Compact FieldPoint>>Controllers>>cFP-2000, FieldPoint>>Controllers/Network Modules>>FP-1000, FieldPoint>>Controllers/Network Modules>>FP-1001, Industrial Communications>>CAN>>FP-1300, FieldPoint>>Controllers/Network Modules>>FP-2000, FieldPoint>>Controllers/Network Modules>>FP-2010, FieldPoint>>Controllers/Network Modules>>FP-2015, Compact FieldPoint>>Controllers>>cFP-2000, Compact FieldPoint>>Controllers>>cFP-2010, Compact FieldPoint>>Controllers>>cFP-2020
Problem: I can find the specifications for module update rate, but I don't understand how the update rate can work with a software-timed FieldPoint Read. What happens when I read the module slower than the update rate? Does the module buffer the data? What if I read the module faster than the update rate? Solution: FieldPoint Read and Write are synchronous with respect to software, but not with the digitizer hardware. A FieldPoint bank behaves much like a network of independent processes. Each module is running its own software loop on its own loop rate. When the FieldPoint controller reads the value from the module, it is actually reading a value from the shared memory of the module. That memory register holds the last successful reading of the channel on the device. The reading of the data from the module has almost no effect on the loop timing. The software acquisition loop on the module runs at a fixed rate, whether the data is being read from the shared memory buffer much faster than it is being acquired, or much slower. In effect, the FieldPoint Read and Write functions are completely asynchronous. This provides a reliable data source, removed from the timing requirements of the sampling. This also means that the samples you receive, while accurate, are not precisely timed. Related Links: Knowledgebase 39AAB2F4: Is My FieldPoint Controller Poll-Driven or Event-Driven? Product Manuals: FP-1000/1001 User Manual Product Manuals: FP-1300 User Manual Product Manuals: FP-2000/2010/2015 User Manual Attachments:
Report Date: 09/05/2003 Last Updated: 10/24/2006 Document ID: 314COE22 |
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