Rockwell Automation 1747-SCNR ControlNet Scanner Module Reference Manual - Manual (Page 37)

Publication 1747-RM623D-EN-P - June 2006
Work with the ControlNet Explicit Message Instruction 4-3
CEM 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 CEM instruction.
• Control Block Length is a display-only field that indicates how
many integer file words are being used by the control block. For
the CEM instruction, the length is always 67 words.
CEM Instruction Setup Screen Parameters
Read these sections for information about the parameters for the CEM
instruction setup screens.
Parameters for this controller on the general tab include the following.
• 1747-SCNR Slot
This drop-down field lists all of the local slots that contain
ControlNet scanner (1747-SCNR) modules within the IO
Configuration. Select the slot number of the particular scanner
that this explicit message will be initiated through.
• Size in Words (Receive Data)
This field defines the size of the integer data file that will be
used to store the data that is returned by this explicit message
command. For best performance, define this file size to only be
as large as is required. If no receive data is expected, you may
leave this field at 0 and no receive data file will be defined. If
unsure of how much data will be returned, you may select up to
the maximum size of 250 words, and then reduce the size later
based on experience.
• Size in Words (Send Data)
This field defines the size of the integer data file that will be
used to store the data that is sent along with this explicit
message command. For best performance, define this file size to
only be as large as is required. If no send data is required, you
may leave this field at 0 and no send data file will be defined. If
unsure of how much data will be sent, you may select up to the
maximum size of 248 words when defining the instruction, and
then reduce the size later based on experience.