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Publish Date: Sep 6, 2006

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DeviceNet Poll Rate

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The poll rate is defined by the Expected Packet Rate parameter, which specifies the expected rate (in milliseconds) of messages (packets) for the I/O connection. After you start communication, the embedded microprocessor on your National Instruments DeviceNet interface transmits messages at the ExpPacketRate. When you select an ExpPacketRate for an I/O connection, you must consider all I/O connections in your system. For example, although you might be able to configure an ExpPacketRate of 3 ms for a single I/O connection, you cannot configure a 3 ms ExpPacketRate for 40 I/O connections, because DeviceNet’s bandwidth capabilities cannot support 40 messages in a 3 ms time frame.

In addition, you must also consider the polling scheme of your DeviceNet network. For a complete description of the requirements of each polling scheme, please consult Chapter 3 of the NI-DNET User Manual.


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This tutorial (this "tutorial") was developed by National Instruments ("NI"). Although technical support of this tutorial may be made available by National Instruments, the content in this tutorial may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this content with each new revision of related products and drivers. THIS TUTORIAL IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).