APPENDIX B – FUNCTION BLOCK MODE – LO
The status of each of the Function blocks can be read by the Host system.
Each block has a minimum of three states taken from the list below:
OOS - Out Of Service
AUTO - Automatic
CAS - Cascade
MAN - Manual
IMAN - Initialise Man mode (Not a permanent condition)
Output blocks may have one other state which is LO - Local. For this to appear, the blocks must be
part of the downloaded configured Function block application.
This mode is entered when the actuator selector switch is either in the Local Stop or Local position,
i.e. when the Monitor Relay bit is true. This mode is also entered when the network disable feature is
chosen for HW_DI-4. See section 5.1. The blocks can also adopt this mode if an illegal data type is
presented to an input.
Fig B.1: Example of LO as seen in an AO block.
In the example for the AO block shown above, values may still be written to the Output of the block. If
the actuator is returned to the Remote Operation state, and the output value is outside the deadband
of the actuator, the valve will be moved to the new position.
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