Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual - Manual (Page 94)

Publication 1747-UM655B-EN-P - June 2007
94 DeviceNet Explicit Messaging
DeviceNet Explicit
Message (DEM) This is an output instruction that lets you initiate unconnected CIP
Generic messages via a 1747-SDN module installed in the local
chassis. These messages can be initiated to any node on the same
DeviceNet network as the 1747-SDN module, as long as the node is in
the scanner’s scanlist. The scanner can be in either Idle mode or Run
mode. Each module can process only one DEM instruction at a time.
The instruction is similar in operation to a standard MSG instruction.
DEM Instruction Parameters
Enter the following parameters when programming this instruction:
•
Control Block is an integer file address that you select. It is a
block of words, containing the status bits and other data
associated with the DEM instruction. It also contains the Send
and Receive data.
•
Control Block Length is a display-only field that indicates how
many integer file words are being used by the control block. For
the DEM instruction, the length is always 70 words.
DEM Instruction Setup Screen Parameters
The following sections provide parameters for the DEM instruction
setup screens.
Parameters for This Controller on the General Tab
•
1747-SDN Slot
This pull-down menu lists all of the local slots that contain
DeviceNet scanner (1747-SDN) modules within the I/O
Configuration. Select the slot number of the particular module
that this explicit message will be initiated through.
•
Size in Send Data (Bytes)
This field defines how many bytes of data are sent along with
this explicit message command. If unsure of how much data will
be sent, you may select up to the maximum size of 52 bytes
when defining the instruction, and then reduce the size later
based on experience.