Chapter 1 NI-DNET Software Overview
© National Instruments Corporation 1-5 NI-DNET User Manual
Much like any other object-oriented system, NI-DNET device driver
objects use the concepts of class, instance, attribute, and service to describe
their features. The NI-DNET device driver software provides three classes
of objects: Interface Objects, Explicit Messaging Objects, and I/O Objects.
You can open an instance of an NI-DNET object using one of the three
open functions (ncOpenDnetExplMsg, ncOpenDnetIntf, or
ncOpenDnetIO). The services for an NI-DNET object are accomplished
using the NI-DNET functions, which can be called directly from your
programming environment (such as Microsoft C/C++ or LabVIEW). The
essential attributes of an NI-DNET object are initialized using its open
function; you can access other attributes using ncGetDriverAttr or
ncSetDriverAttr. The attributes of NI-DNET device driver objects are
called driver attributes, to differentiate them from actual attributes in
remote DeviceNet devices.
For complete information on each NI-DNET object, including its driver
attributes and supported functions (services), refer to your NI-DNET
Programmer Reference Manual.
Interface ObjectThe Interface Object represents a DeviceNet interface (physical DeviceNet
port on your DeviceNet board). Since this interface acts as a device on the
DeviceNet network much like any other device, it is configured with its
own MAC ID and baud rate.
Use the Interface Object to do the following:
• Configure NI-DNET settings that apply to the entire interface
• Start and stop communication for all NI-DNET objects associated with
the interface
Explicit Messaging ObjectThe Explicit Messaging Object represents an explicit messaging
connection to a remote DeviceNet device (physical device attached to your
interface by a DeviceNet cable). Since only one explicit messaging
connection is created for a given device, the Explicit Messaging Object is
also used for features that apply to the device as a whole.
Use the Explicit Messaging Object to do the following:
• Execute the DeviceNet Get Attribute Single service on the remote
device (ncGetDnetAttribute)