About Devicenet - Graco 15V963 Instructions Manual

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Appendix A: DeviceNet Slave Communication

About DeviceNet

DeviceNet is a connection-based network. In this con-
text the term connection refers to a communication path
between two or more devices, and not the physical
(cable) connection to the DeviceNet network. A connec-
tion must be established between two devices in order
to transfer data.
There are two types of connection defined by the Devi-
ceNet specification. Each has different characteristics
and is suited to a specific type of communication.
• I/O Connection – Dedicated data transfer between
a producer and one or more consumers. The format
of the data is known or implied by the connection.
• Explicit Messaging – Generic multi-purpose mes-
saging connection, typically command and
response message commands.
Each connection type has an extensive number of
parameters, which can affect the characteristics of the
communication path. For many Master/Slave communi-
cations scenarios, a defined set of connections, together
with their respective parameter settings exist under the
collective name Predefined Master/Slave Connection
Set. Many of the steps involved in creating and configur-
ing a connection have been removed with this connec-
tion set, thus simplifying the network configuration.
Predefined Master/Slave Connection Set
The DeviceNet specification details a number of con-
nections that facilitate data transfer between a Master
and Slave devices. The following sections detail the con-
nection types supported by the Gateway.
• I/O Bit-Strobe Connection: The Bit-Strobe connec-
tion is an I/O connection over which Bit-Strobe I/O
command and response messages are transferred.
The Bit-Strobe command is broadcast by the Master
device and is received by all slave devices simulta-
neously. The command message contains a single
bit of information for each slave on the network.
Each slave device is required to respond with a Bit-
Strobe response message. The response message
can contain up to 8 bytes of information.
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• I/O Poll Connection: The Poll connection is an I/O
connection over which Poll command and response
messages are transferred. The Poll command is
transmitted by the master, and is directed to a single
slave device. The slave device in turn responds with
a Poll response message. Both the Poll command
and Poll response messages can contain any num-
ber of bytes.
• I/O Data Connection: The I/O Data connection is
part of the Predefined Master/Slave Connection Set,
but instead is included for devices, which support
creating I/O data connections via the UCMM
(Unconnected Message Manager).
Level of Support
The Gateway provides Group 2 Server level support: A
UCMM capable device that is configured to act as a
Slave for the Predefined Master/Slave connection set.
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