Contrary to the motion commands, retriggering of a MC_TouchProbe or MC_AbortTrigger instance does not lead to an overwriting of the previous command, but instead, the new command is discarded by the FB and no new command is sent. The retriggered FB instance indicates an FB-specific error and remains ACTIVE. At the FB outputs "Error’ and ‘ErrorID’, a signal is output for one PLC cycle with which retriggering can be detected. If either AXIS_REF or die TRIGGER_REF has changed at the time of retriggering, this is indicated as an error at the aforementioned function block outputs and the command is also rejected.
The "CommandAborted" output can only be set if the command has been explicitly aborted by an MC_AbortTrigger. To abort a measurement command, it must use the identical measurement channel number and mode in TRIGGER_REF, because a measurement command is exclusively identified based on agreement of all TRIGGER_REF parameters.
Contrary to the motion commands, a measurement command does not lead to a change in the axis status. As PLCopen does not specify in what states MC_TouchProbe is permissible, it is defined that this is permissible in all states except ‘ERROR_STOP’ and ‘HOMING’.
For a measurement channel a separate state diagram is used. The current state is administered in ‘tp_state’ of the AXIS_REF structure of the axis, that was commanded with the measurement instruction.
Fig.2: State diagram of a measurement channel
Thus, a maximum of as many measurement commands is possible as there are axes available.
Fig.2: State diagram of a measurement channel