PLCopen General Rules - Output Exclusivity

If the Execute input of a function block is set TRUE, either the Busy, Done, Error, or CommandAborted outputs must also be set TRUE. These outputs are mutually exclusive, meaning that a function block may have only one of them set TRUE at any time.

The output functionality of the MC_GearOut function block is an exception to this exclusivity rule. The MC_GearOut is done when the slave axis is disengaged from the master axis. Unlike most other motion function blocks, once done, the MC_GearOut will remain busy and active until it is aborted by a different motion function block. The MC_GearOut function block represents an exception to the exclusivity rule as the Done and Active outputs may be true at the same time.