Rockwell Automation GMLC Reference Manual - Manual (Page 350)

Publication GMLC-5.2 - November 1999
Watch Control 313
The Watch Control block, with Arm type and Watch Position class
selected, sets up a watch position event that occurs when the selected
physical or imaginary axis reaches the specified position.
You can use watch position events to synchronize an operation to a
specific axis position while the axis is moving, such as activating a
solenoid to push a carton off a conveyor at a certain axis position.
When a Watch Control block with Arm and Watch Position selected
executes the following:
• the Watch_Pos_status variable for the axis is set to 0 (false)
• the actual position of a physical axis or the command position of the
imaginary axis is monitored (at the servo loop update rate) until it
reaches the specified setpoint (watch) position
After the watch position event occurs, the Watch_Pos_status variable for
the axis is 1 (true).
You can include multiple watch position events in a single program—but
only one for each physical or imaginary axis on the motion controller.
Each event is monitored independently and may be checked using the
appropriate Watch_Pos_status variable.
Watch
Position
Event
Set Up
Axis Position
Watch_Pos_status
Setpoint
Position
0
1
+ –
Watch
Position
Event
Occurs