Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 173)

7–52 Creating Messages
Publication 2706-817
Example 2: A Maintained Function Key that has been pressed only
once remains in the changed state after the message is terminated. It
may be returned to its original state in either of two ways.
•
Enable jog mode by disabling the Auto Clear attribute. The
message tells the operator to press and release the Function key
twice.
•
Chain or trigger another message that has the same Function key
enabled. The second message tells the operator to press the
Function key again.
The LED located beside the Function key may or may not have its
Indicator tag defined. LEDs may be used in any application designed
for a MessageView 421F terminal. See Page 4–25 for a discussion of
LEDs.
When the application is designed, make a list of the LEDs to be used
and note which ones need an Indicator tag defined. Set them all up
before any messages are created.
Important: LED attributes are global.
•
When an LED does not have a tag assigned to it, the LED has no
tag any time it is used in the application.
•
When a LED is assigned a certain tag, that tag remains assigned
to it throughout the application.
When the LED does not have an Indicator tag assigned to it, then the
LED follows the state of the associated Function key (LED1 with F1,
LED 16 with F16). For example, LED4 will light when Function key
F4 is pressed, and LED4 remains lit for the duration of the Function
key’s On state while the message associated with the Function key is
actively displayed.
When the LED has an Indicator tag assigned to it, the LED operates
independently of the associated Function key. For example, pressing
and releasing Function key F1 will have no effect on the operation of
LED1. The controller logic program controls the LED by setting or
clearing the bit at the Indicator tag address. Thus the controller can
indicate a process status without displaying a message.
Note: All assigned LED tags are monitored on a continuous basis
except when the terminal is in its Front Panel Editor mode.
LED Attributes