National Instruments NI-DNET Chapter 4 NI-DNET Programming Techniques, Appendix A DeviceNet Overview

Contents
NI-DNET User Manual vi ni.com
Programming Model for NI-DNET Applications......................................................... 3-6
Step 1. Open Objects.......................................................................................3-8
Step 2. Start Communication..........................................................................3-8
Step 3. Run Your DeviceNet Application.......................................................3-8
Addition of Slave Connections after CommunicationStart ............. 3-9
Step 4. Stop Communication.......................................................................... 3-10
Step 5. Close Objects......................................................................................3-10
Multiple Applications on the Same Interface................................................................3-10
Checking Status in LabVIEW.......................................................................................3-11
Checking Status in C, C++, and Visual Basic...............................................................3-11
Chapter 4
NI-DNET Programming Techniques
Configuring I/O Connections........................................................................................4-1
Expected Packet Rate......................................................................................4-1
Strobed I/O.......................................................................................4-2
Polled I/O..........................................................................................4-3
Cyclic I/O.........................................................................................4-6
Change-of-State (COS) I/O.............................................................. 4-7
Automatic EPR Feature..................................................................................4-7
Using I/O Data in Your Application............................................................................. 4-8
Accessing I/O Members in LabVIEW............................................................4-10
Accessing I/O Members in C..........................................................................4-11
Using Explicit Messaging Services...............................................................................4-12
Get and Set Attributes in a Remote DeviceNet Device.................................. 4-12
Other Explicit Messaging Services.................................................................4-13
Handling Multiple Devices............................................................................................4-14
Configuration..................................................................................................4-14
Object Handles................................................................................................4-15
Main Loop.......................................................................................................4-16
Appendix A
DeviceNet Overview
History of DeviceNet.....................................................................................................A-1
Physical Characteristics of DeviceNet..........................................................................A-2
General Object Modeling Concepts..............................................................................A-2
Object Modeling in the DeviceNet Specification..........................................................A-3
Explicit Messaging Connections...................................................................................A-5
I/O Connections.............................................................................................................A-7
Assembly Objects..........................................................................................................A-11