Allen-Bradley DeviceNet 1761-NET-DNI, User Manual, Page: 85 / 101

1761-6.5
Chapter
8
Explicit Messaging (DNI Series B Only)
Explicit messaging is the mechanism that is used to move data over
DeviceNet. Every device on DeviceNet either initiates or responds to some
type of explicit message to either read (get) or write (set) data.
In the network shown below, node 5 is a master (scanner) that owns slave
I/O data on the DeviceNet network. When the master interacts with its
slaves (either through strobed, polled, cyclic or COS connections), the
communications used are specific types of I/O messages. If the MicroLogix
controllers at nodes 10 and 30 want to exchange data, they message through
the DNIs to each other using explicit messages.
The functionality of each device determines how it can interact with other
devices on the network. Many devices can only respond to requests. Some
devices can be configured to respond, but they can also initiate messages to
others. One example is the PanelView operator interface that has DeviceNet
built in. It can be owned by a master as slave I/O, and can also get or set data
to other devices on the network.
Node 5
Node 15
Node 25
Node 30
Node 20
Node 10
AB Parts