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ICP DAS USA I-7242D User Manual Page 24

Devicenet / modbus rtu gateway.
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have been established, I/O data may be moved among devices in the network.
The 11-bit CAN identifier is used to identify the connection. DeviceNet
defines four separate groups of 11-bit CAN identifiers: Group 1, Group 2,
Group 3, and Group 4 described in the Table 3-1. With respect to Connection
Based Messages, the Connection ID is placed within the CAN Identifier Field.
With this in mind, the below figure also describes the components for a
DeviceNet Connection ID. Because of the arbitration scheme defined by CAN,
Group 1 messages have a higher priority than group 2 messages and group 2
messages have higher priority than group 3 messages and so on. This
prioritization must be taken into consideration when establishing connections.
Table 3-1 DeviceNet's Use of the CAN Identifier Field
IDENTIFIER BITS
10
9
8
7
6
5
Group 1
0
Source MAC ID
Message ID
1 0
MAC ID
Group 3
1 1
Message ID
1 1 1 1 1
Group 4 Message ID
The I-7242D provides the Predefined Master/slave Connection Set for
users to establish connections. The Predefined Master/Slave Connection Set
is a set of Connections that facilitate communications typically seen in a
Master/Slave relationship. Many of the steps involved in the creation and
configuration of an Application connection have been removed within the
Predefined Master/Slave Connection Set definition. This, in turn, presents the
means by which a communication environment can be established using less
network and device resources. The CAN Identifier Fields associated with the
Predefined Master/Slave Connection Set are shown in the table 3-2. The table
defines the Identifiers that are to be used with all connection based message
involved in the Predefined Master/Slave Connection Set and, as such, it also
illustrates
the
attributes associated with Predefined Master/Slave Connection Objects.
Note: The Master is the device that gathers and distributes I/O data for the
process controller. Slaves are the devices from which the Master gathers I/O
data and to which the Master distributes I/O data.
I-7242D DeviceNet/Modbus RTU Gateway User's Manual, July 2006, Version 1.1
4
3
2
1
0
Group 1 Messages
Group 2
Group 2 Messages
Message ID
Source MAC ID
Group 3 Messages
Group 4 Messages
produced_connection_id
I-7242D user manual
IDENTITY USAGE
and
consumed_connection_id
HEX
RANGE
000 –
3ff
400 –
5ff
600-7bf
7c0–7ef
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