Rockwell Automation 1761-NET-DNI DeviceNet Interface (DNI) - Manual (Page 78)

Publication 1761-UM005B-EN-P - October 2006
78 Explicit Messaging (DNI Series B Only)
The Series B DNI also has the ability to exchange data with other
DeviceNet devices using explicit messaging, provided those devices
are capable of interacting. The following list provides some of the
requirements.
• If a device is Unconnected Message Manager (UCMM) capable,
it should be 100 percent compliant with or without a master
being present on the network.
• If a device is not UCMM capable, it will need a master to be
present on the network, and it should be owned by the master.
• If a device is not UCMM capable and a master is not present (or
a master is present but the device is not owned by the master),
the device will not be compatible with the DNI using explicit
messaging.
Using DF1 Protocol for
Explicit Messages Over a
DeviceNet Network The DNI is an intelligent bridge between DF1 full duplex
(Allen-Bradley open protocol) and DeviceNet. All Allen-Bradley
controllers that use DF1 protocol (basically any Allen-Bradley
controller with an RS-232 port) use the historical source/destination
model to move data.
The problem with this is that DeviceNet technology uses the newer
producer/consumer model and is not compatible with the
source/destination model. So, to allow controllers that use the
source/destination model (MicroLogix, SLC, PLC) access to devices on
the DeviceNet network, the DNI can act as an intermediary.
To act as an intermediary, the DNI must allow the historical DF1
message format to be compatible with the newer DeviceNet
producer/consumer object model. This is accomplished by creating a
routing profile. The routing profile basically takes the DF1 message
and converts it to DeviceNet. Each routing profile contains the
information needed to get or set data to other DeviceNet devices.
Each routing profile has the following five components.
• Node - the address of the Device on a DeviceNet network
• Class - the DeviceNet class code
• Instance - the DeviceNet instance code
• Attribute - the DeviceNet attribute code
• Size - the amount of data to be read or written