Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual - Manual (Page 93)

93 Publication 1747-UM655B-EN-P - June 2007
Chapter
8
DeviceNet Explicit Messaging
DeviceNet Explicit
Message Instruction
Overview The DeviceNet Explicit Message (DEM) instruction allows generic
Common Industrial Protocol (CIP) commands to be initiated to
devices, such as drives, communicating on DeviceNet networks. This
instruction requires RSLogix 500 software, version 7.10 or later, for
programming.
The DEM instruction utilizes the explicit message capability built into
the 1747-SDN DeviceNet scanner module.
While not adding any additional capability over what already exists in
the scanner module, the DEM instruction greatly simplifies the
programming, configuration, monitoring, and troubleshooting of
explicit messages on the DeviceNet network.
Unlike I/O configured in the scanner module’s scanlist, which is
updated on a continual basis, explicit messages allow data to be sent
and received on an as-needed basis, minimizing network traffic. For
instance, you may only want to write configuration parameters to a
drive once at machine start-up time.
The DEM instruction can be used with any SLC 5/03, SLC 5/04, or
SLC 5/05 processor that is at OS firmware level Series C, FRN 10 or
later.
The DEM instruction uses an integer control block for storing the
instruction parameters and a configuration setup screen, similar to the
MSG instruction. The CIP commands consist of a Service Code; the
object Class, Instance, and Attribute; and Send and Receive Data (if
required for the selected Service Code). The setup dialog provides a
list of standard CIP Services to select from, including:
•
Read Assembly.
•
Write Assembly.
•
Read Parameter.
•
Write Parameter.
•
Generic Get Attribute Single.
•
Generic Set Attribute Single.
In addition, a Custom setting lets you enter any Service Code. Send
data and receive data are stored in separate data table files.