Read and Write Queues for Frame API in NI-CANHardware: Industrial Communications
Problem: I have configured a read or a write queue in NI-CAN and I notice that the Read Entries Pending or Write Entries Pending property is higher than the specified queue. How do these queues work? Solution: The read and write queues in the frame API network interface are used to transfer frames from shared memory to a seperate queue managed by the NI-CAN driver. When using the network interface, using the ncConfigCANNet VI, a read queue can be specified. The NI-CAN driver automatically transfers frames from this read queue in shared memory to a second, larger queue that is maintained automatically. This second queue does not have the same size as the read queue configured by ncConfigCANNet.vi. There is no way to configure how large the secondary queue or how often the read or write queue transfers information between shared memory and the queue maintained by NI-CAN. When using objects in frame API, the read and write queues specified by ncConfigCANObj.vi are the maximum number of frames that can be stored for that CAN object. If those queues fill, you will receive an overflow error. The Read Entries Pending and Write Entries Pending will return the number of frame in the queue maintained by the driver which is larger than the read or write queue specified in the network object. Related Links: KnowledgeBase 1YL9E1RM: What Causes Queue Overflow with NI-CAN? KnowledgeBase 18M9O8TI: How can I solve an NI-CAN read buffer overflow error? Attachments:
Report Date: 05/29/2009 Last Updated: 05/29/2009 Document ID: 4XSAJ83Q |
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