Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 73)

4–25 Planning an Application
Publication 2706-817
MessageView 421F terminals have a red LED located next to each
function key. Each LED may or may not have an Indicator tag
assigned to it.
Indicator tags are globally defined in the LED dialog.
•
When a LED is assigned a certain tag, that tag remains assigned
to it throughout the application.
•
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 the LED does not have an Indicator tag assigned to it, 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. LED4 remains lit as long as the Function key is in the
On state and the message displayed remains active.
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 program turns the LED On and Off by setting
or clearing the bit at the Indicator tag address. Thus the logic
controller can indicate a process status to the operator without
displaying a message.
➀ ➀
No Indicator Tag Indicator Tag
➁➂
➃
Step Description
➀
➁
➂
Bit set to 1 in F-key
Function Key pressed
LED changes state
Step Description
➀
➁
➂
➃
Bit at Indicator Tag address
set by logic controller
➂
Write Tag address
based on bit read from
INITIAL
STATE
ООО
ООО
ООО
NEXT
STATE
INITIAL
STATE
ООО
ООО
ООО
NEXT
STATE
➁
Write Tag address
Function Key pressed
Bit set to 1 in F-key
Write Tag address
LED changes state
based on bit read from
Indicator Tag address
LED Indicators