B&B Electronics GW-7472 - Manual - Manual (Page 37)

GW-7472 User Manual, Version 1.0, Dec 2010 --- 37
5. R/W Modbus RTU devices from EtherNet/IP
Since the GW-7472 provides the functions of an EtherNet/IP adapter and Modbus RTU
master, there are some mechanisms for data-exchanging between EtherNet/IP objects and the
Modbus RTU registers. This section describes the EtherNet/IP Object Model of the GW-7472
and how to read/write the GW-7472 EtherNet/IP object data mapping to the registers of Modbus
slaves by using the EtherNet/IP Explicit and Implicit Message.
5.1 Object Model
The Object Model for the GW-7472 is shown in the following figure. Inside the GW-7472,
there are one Modbus RTU master and an EtherNet/IP adapter. When booting up, the GW-7472
scans all of the input registers of Modbus RTU slaves and updates all of the output registers of
Modbus RTU slaves. At the same time, the Modbus RTU master exchanges the input data and
Modbus connection conditions with the objects of the EtherNet/IP adapter.
The EtherNet/IP adapter of the GW-7472 provides six kinds of objects. Each object has
its characteristic, service and instances. The Connection Manager Object is applied for building
a connection before using the Explicit Messages and the Implicit Messages. The Message
Router Object is used to route the message to other objects of the EtherNet/IP adapter. The
Assembly Object, Identity Object, TCP/IP Object, and Ethernet Link Object are used to record
the I/O information, device information, TCP/IP configuration, Ethernet link-specific status
information respectively. After receiving an EtherNet/IP message, the GW-7472 will distinguish
what the message type it is. The Explicit Message can direct access the Assembly Object or
access other objects via the Message Router Object. The Implicit Message can only access I/O
data of the Assembly Object. The UCMM Message is used to access all of the objects without
building a connection. When the UCMM Message is got by the GW-7472, the message is
passed to the Message Router Object for routing. When the EtherNet/IP scanner communicates
with the EtherNet/IP adapter of the GW-7472, the GW-7472 replies the corresponding
information. At the same time, the EtherNet/IP adapter exchanges the output data with the
Modbus master.