Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 50)

4–2 Planning an Application
Publication 2706-817
The application designer must make sure that an application cannot
be used in an unsafe manner. Failsafes must be built into each
application.
!
ATTENTION: Do not configure Function Keys as
emergency stops or other controls critical for safe
operation. Use separate hard-wired operator interface
devices.
Refer to “Safety Guidelines for the Application, Installation and
Maintenance of Solid State Controls” (Publication SGI-1.1).
Communications interruptions
The MessageView 421 terminal relies on communications with the
logic controller or ASCII Triggering device.
•
Communications are interrupted within the terminal when it:
– is in the Front Panel Editor mode
– is receiving an application download from a personal
computer
– has a major fault
– loses power
– detects that the Remote I/O link has failed.
The logic controller considers the terminal as a faulted I/O rack
when it does not communicate. The controller must be programmed
to cope with this situation. Specifically, it must:
•
return any machine or process to a safe state
•
monitor the rack fault bit associated with the MessageView
terminal’s assigned rack.
Refer to the controller’s user manual.
Safety Considerations