Rockwell Automation 2706 DL40 HARDWARE USER MANUAL - Manual (Page 34)

Chapter 3
The Run Mode – Remote I/O
3 – 8
possible that messages with low priorities may never be displayed. After the
DL40 has displayed all the messages in the Priority Section (with bits set),
the messages in the Round Robin Section will be displayed.
Note: The size (in words) of the Priority Section is set with the Onboard
Editor or with the Offline Programming Software.
Round Robin Section
Messages with trigger bits set in this section will be run after the Priority
Message and all messages in the Priority Section with bits set have been run.
The DL40 will run through this section displaying messages. After the last
message in this section has been displayed, the DL40 will go back to the first
message (in this section) and start again. Messages will continue to run until
an updated Bit Trigger Table is sent. After all priority messages in the
updated Bit Trigger Table have been run, the DL40 will return to where it left
off in the Round Robin Section and continue on from there.
Length of the Round Robin Section in (16 bit) words is:
•
the length of the Bit Trigger Table – 32 words
•
minus the Priority Message – 1 word
•
minus the Length of the Priority Section – X words
Note: The lengths of the Priority Message, the Priority Section, and Round
Robin Section are always in full (16 bit) words.
For example, If the Priority Section is 9 words long, then the length of the
Round Robin Section would be:
32 words
–1 word
–9 words
= 22 words
In this mode, you can also:
Return the Message Number of the Message Being Run to a PLC
This is automatically done in the Remote I/O scan.
Insert ASCII Input Data into a Message
Same as Message/Variable/Slave Run Mode; except only returns data to a
PLC via RS-485 Port.
Note: If the message Historical Event Stack Attribute is set, data is put on
Historical Events Stack.