Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 58)

4–10 Planning an Application
Publication 2706-817
From a logic controller using Remote I/O
The MessageView terminal supports a Value Trigger tag in the PLC
or other logic controller. When a message is to be triggered, the logic
controller writes the message number to this tag address.
Only one message may be value-triggered at a time. The terminal
scans the Value Trigger tag address at regular intervals. A triggered
message number must remain stable in the Value Trigger tag address
for a minimum of 100 milliseconds, to allow for the terminal scan
times.
The message is not triggered again until the value in the Value
Trigger tag address is changed to a different number and then
changed back. Thus the ladder logic application designer may use a
message number of 0 (zero) to change the Value Trigger tag address
without triggering a message.
From an ASCII Triggering Device using RS-232
The MessageView terminal supports the triggering of messages
using the Value Trigger method. The format of this method is:
[Ctrl-T]Message Number\MessageView Address[CR]
•
[Ctrl-T] is the control code for a command to the terminal
•
Message Number is the value trigger for the message
•
MessageView Address is the node in the network where the
terminal is located
•
[CR] is the carriage return that ends a packet.
Note: The delimiter in ASCII triggering packets uses the backslash \.
In order to trigger a message, the ASCII Triggering Device transmits
a [Ctrl-T] packet sequence. When the terminal receives this packet, it
displays or queues the message.
Note: A MessageView terminal in an ASCII network that has an
address from 1 to 126 will respond to messages addressed to it, and
also to messages addressed to 127. A terminal with an address of 127
will respond to messages addressed to 127 only.