Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 68)

4–20 Planning an Application
Publication 2706-817
A MessageView 421F terminal supports 16 Function keys (F1 to
F16) and 16 LEDs on the front panel.
A typical message with Function keys enabled informs the operator
the intended function of each enabled function key. For instance:
F1 Start F2 Stop Pump
Pressing a Function key sets or clears a bit value assigned to the
Function key’s write tag address. The controller logic program can
use the write tag address for a variety of control operations such as a
machine’s start and stop functions.
!
ATTENTION: Do not use a MessageView terminal
for emergency stops or other controls critical for the
safety of personnel or equipment. Use separate
hard-wired operator interface devices.
Global attributes
Individual Function key attributes are globally defined. For instance,
if F1 is defined as momentary, every time it is enabled for a message
it is a Momentary Function Key. If a Latched Function Key is
needed, you must enable a different key.
The MessageView terminal supports three types of Function key
operations as global attributes:
•
momentary
•
maintained
•
latched.
See the section on each type starting on Page 4–23. Other global
attributes are discussed in these sections.
Function Keys