National Instruments NI-DNET - Manual (Page 15)

Chapter 1 NI-DNET Software Overview
NI-DNET User Manual 1-6 ni.com
• Execute the DeviceNet Set Attribute Single service on the remote
device (
ncSetDnetAttribute )
• Send any other explicit message request to the remote device and
receive the associated explicit message response
(
ncWriteDnetExplMsg , ncReadDnetExplMsg )
• Configure NI-DNET settings that apply to the entire remote device
I/O Object
The I/O Object represents an I/O connection to a remote DeviceNet device
(physical device attached to your interface by a DeviceNet cable). The
I/O Object usually represents I/O communication as a master with a remote
slave device, but it can also be used for I/O communication as a slave.
The I/O Object supports as many master/slave I/O connections as currently
allowed by the DeviceNet Specification. This means that you can use
polled, strobed, and COS/cyclic I/O connections simultaneously for a given
device. As specified by the DeviceNet Specification, only one master/slave
I/O connection of a given type can be used for each device (MAC ID). For
example, you cannot open two polled I/O connections for the same device.
Use the I/O Object to do the following:
• Read data from the most recent message received on the
I/O connection (
ncReadDnetIO )
• Write data for the next message produced on the I/O connection
(
ncWriteDnetIO )
Example
Figure 1-2 shows an example of how NI-DNET objects can be used to
communicate on a DeviceNet network. This example shows three
DeviceNet devices. The first device (at MAC ID 1) is the National
Instruments DeviceNet interface. The second device (at MAC ID 5) uses
NI-DNET to access a polled and a COS I/O connection simultaneously.
The third device (at MAC ID 8) uses NI-DNET to access an explicit
messaging connection and a strobed I/O connection.