Rockwell Automation 1771-QB Linear Pos. - Manual (Page 143)

Advanced Features
Chapter 9
9-12
As mentioned previously, because initiating a single motion segment from
the command block can trigger a sequence of motions, you must exercise
caution when using the motion block. For safety reasons, a watchdog
monitors the state of the programmable controller. If it faults or enters
programming mode while a motion segment is executing, the watchdog in
the module initiates a slide stop. The programmable outputs in the motion
block will be set to either their last state or to reset state, depending on how
bit 8 (programmable outputs reset/fault state) in the programmable I/O
word is configured.
Important: When the module is reset with the command block,
previously defined motion segment and setpoint data is lost, but the
programmable I/O configuration remains as it was prior to axis reset. If
power is cycled, the programmable I/O configuration changes to its
default.
Here are some recommended ways of stopping axis motion while motion
segments are active. The one you use will depend upon your particular
application.
perform a slide stop (software)
execute an immediate stop (hardware or software)
initiate a setpoint (the final axis position will be the setpoint’s endpoint)
initiate a motion segment which will not have its trigger conditions
satisfied (the final axis position will be at the motion segment’s
endpoint)
put the programmable controller in programming mode
Important: When a motion segment is commanded with the hardware
start enabled, hardware starts are automatically accepted during axis
motion regardless of the Stop/Start enhancement setting (axis control word
1 in the command block). When you initiate a motion segment with the
hardware start enabled in the command block, the specified motion
segment will not begin execution until the module recognizes a rising edge
on the hardware start input. However, subsequent motion segments
triggered by another motion segment will not require a hardware start to
begin execution.
Using the Motion Block