88 Rockwell Automation Publication 2080-UM002G-EN-E - March 2015
Chapter 7 Motion Control
On a non-continuous motion, to prevent a moving axis going to ErrorStop status
with Motion PTO Pulse limits detected, user needs to prevent current position
value going beyond PTO Pulse limit.
On a continuous motion (driven by MC_MoveVelocity function block), when
the current position value goes beyond PTO pulse limit, PTO pulse current
position will automatically roll over to 0 (or the opposite soft limit, if it is
activated), and the continuous motion continues.
For a continuous motion, if the axis is homed, and the soft limit in the motion
direction is enabled, soft limit will be detected before PTO pulse limit being
detected.
Motion Stop
There are three types of stops that can be configured for an axis.
Immediate Hardware Stop
This type of Immediate Stop is controlled by the hardware. If a Hard Stop on a
Hard Limit switch is enabled, and the Hard Limit has been reached, the PTO
pulse for the axis will be cut off immediately by the controller. The stop response
has no delay (less than 1 μs).
Immediate Soft Stop
The maximum possible response delay for this type of stop could be as much as
the Motion Engine Execution time interval. This type of stop is applicable in the
following scenarios:
• During motion, when axis PTO Pulse Limit is reached;
• One Hard Limit is enabled for an axis, but Hard Stop on Hard Limit
switch is configured as Off. If the Emergency Stop is configured as
Immediate Software Stop, during motion, when the Hard Limit switch is
detected;
• One Soft Limit is enabled for an axis and the axis has been homed. If the
emergency stop is configured as Immediate Soft Stop, during motion,
when the Soft Limit reach is detected;
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