ABB 800xA Operation page 26

Exception Handling
Block Update of Inputs
Blocking of inputs and outputs should never be used for safety critical signals as
this will jeopardize the safety system function. Safety outputs in blocked mode
are reported in the Safeguard System status display
Outputs in Manual Mode
If the outputs are accessible for operator control under normal operation, the use of
manual mode should be given special consideration.
The manual mode state of objects is included in the dual start-up synchronization to
ensure that the database contents of the two nodes are equal at start-up.
To notify the operator about objects in manual mode, the Quick List aspect can be
used occasionally to search for such objects and print or display them on screen.
Safety outputs should not be set in manual mode as this will jeopardize the safety
system function. Safety outputs in manual mode are reported in the Safeguard
System status display but are not covered by the channel test
Blocking of Outputs
The blocked state of output signals is included in the dual start-up synchronization
to ensure that the database contents of the two nodes are equal at start-up.
To notify the operator about blocked outputs, the Quick List aspect could be used
occasionally to search for such objects and print or display them on screen.
Blocking of outputs must never be used in safety applications as this will reduce
the availability of the system. If the property OUTP_BLK=1 at dual start -up
synchronization, the concerned DO-board channel is not updated with VALUE
from the database. This could lead to a discrepancy between the physical outputs
in the two controllers.
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Section 2 Operation
3BNP004849-600