Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 71)

4–23 Planning an Application
Publication 2706-817
Momentary Function Keys
A Momentary Function Key remains in a changed state as long as
the key is pressed. When it is released, after a preset Hold Time has
expired the key changes back to its original state. The Hold Time
value represents a brief delay in which the control function remains
active after the operator releases the Function key. This Hold time is
set in the Function Keys dialog, which is accessed through a
command on the Application menu.
The MessageView terminal supports Hold Times of 0, 50, 250, 500,
750 or 1000 milliseconds.
A Momentary Function Key does not have a definitive handshake
tag.
!
ATTENTION: If communication with the logic
controller uses Remote I/O protocol with block
transfer, the Function key write tags must all be
assigned to the same block as the Function Key Return
Message Number tag.
Maintained Function Keys
A Maintained Function Key changes state (0 to 1, or 1 to 0) when
pressed, and remains in the changed state when released. It returns to
its original state when the function key is pressed and released again.
A Maintained Function Key retains its current state after the message
is terminated.
Since a Maintained Function Key toggles between two states, its
Initial state (0 or 1) must be specified independently of its Contact
Normally Open/Normally Closed state. The initial state of a
Maintained Function Key after a powerup or terminal reset depends
on the Values At Startup attribute, which is set in the Terminal Setup
Advanced Dialog.
•
Preset: the Function key’s state at startup is the same as its initial
state, set in the application.
•
Last: the Function key’s state at startup is its last state before the
power down or reset.
A Maintained Function Key does not have a definitive handshake
tag.
!
ATTENTION: If communication with the logic
controller uses Remote I/O protocol with block
transfer, the function key write tags must all be
assigned to the same block as the Function Key Return
Message Number tag.
Function Key Types