Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 60)

4–12 Planning an Application
Publication 2706-817
Bit triggering
This method uses bits within a designated word of memory, the Bit
Trigger tag address, to trigger messages. The Bit Trigger tag is
defined in the Terminal Setup dialog (see Page 10–21). Starting with
this tag address, you may reserve up to 64 words (1024 bits) in
sequence for all the bit triggers in the application.
If the system uses Remote I/O to transfer data, the maximum number
of bit triggers may be reduced.
RIO Method Rack Size
Maximum # of Bit
Triggers
Discrete I/O 1 /
4
32
Discrete I/O 1 /
2
64
Discrete I/O 3 /
4
96
Discrete I/O Full 128
Block Transfer 1 /
4
to Full 1024
When the Bit Trigger attribute is enabled for a message, its bit is also
assigned. Only one message may be assigned to a particular bit
address.
When a message is to be bit triggered, the logic controller writes a 1
to a specific bit at the Bit Trigger tag address.
•
When the logic controller resets the bit to 0, the corresponding
message is not displayed.
•
When the logic controller sets the bit to 1, the terminal displays
the message if its assigned display line is available.
Important: If its line is not available and the bit remains set
(1), the terminal will display the message when
the corresponding line becomes available.
If the bit is reset to 0 before the line is available, the terminal will
ignore the message.
•
In order to trigger the same message again, its corresponding bit
must be changed to 0 and back to 1.
Note: Any message that has its HE Stack or slave attribute set, is
sent to the Historic Event Stack or the slave device when it is
triggered. The message does not have to be displayed.