Halts Overview

Halts stop motion on an axis. Halts will also stop any Tasks that are running, if the Programming Properties are set to do so. The RMC has four types, or levels, of halts to safely stop the axis in various circumstances. These halts are well-suited for use when error conditions occur. The RMC, by default, triggers a halt when any Error Bits turns on.

Tip:
The Halts do more than just stop the axis. If you simply wish to stop the motion in closed loop control, use the Stop (Closed Loop) (6) command instead. If you wish to stop the motion in open loop control, use the Stop (Open Loop) (22) or Open Loop Rate (10) commands.

Halt Types

The RMC has four types of halts:

External Halt
This halt only sets External Halt status bit. This halt type is intended to signal the PLC to initiate its fault handling.
Closed Loop Halt
The axis stays in closed loop and ramps down the Target Velocity to zero at the rate specified by the Closed Loop Halt Deceleration parameter. If an axis is in Open Loop, this halt will automatically be promoted to an Open Loop Halt.
Open Loop Halt
The axis will be put in open loop and the Control Output will be ramped down to the value of the Output Bias parameter using the Open Loop Halt Ramp parameter.
Direct Output Halt
The axis will be put in Direct Output and the Control Output will be ramped down to the value of the Output Bias parameter using the Open Loop Halt Ramp parameter. When the Control Output reaches the Output Bias, the Enable Output will be turned off.
Disable Axis Halt
The axis will be disabled so that it will not accept any motion commands, will be put in Direct Output, and the Control Output will be ramped down to the value of the Output Bias parameter using the Open Loop Halt Ramp parameter. When the Control Output reaches the Output Bias, this halt turns off the Enable Output.

Halt Actions

When a halt occurs on an axis, the RMC takes the following actions:

The axis begins the halt, as specified above.

When a halt other than an External Halt occurs on an axis, the Halted status bit is set and the axis is said to be halted. If an External halt occurs, the External Halt status bit is set instead.
If the axis is part of a Halt Group, it starts the same level of halt on all axes in the group. See the Halt Group Number topic for more details.
The RMC immediately stops all Tasks by default. This setting can be changed on the Programming Properties dialog.

Caution:
If you disable this feature, User Programs may still be running after a halt occurs and may cause motion on the axis. Make sure you handle the halt condition safely. One method is to create a User Program to handle the halt condition and use the Program Triggers to start the User Program when the Halt bit turns on.

Pressure/Force Control

The Closed Loop Halt and Open Loop Halt do remove the axis from pressure or force control. The Direct Output Halt (3) and Fault Controller (8) commands will.

Triggering a Halt

Halts can then be triggered in two ways:

Issue a Command
By issuing commands (except External Halt). See each halt command topic for details.

Halt	Command
Closed Loop Halt	Closed Loop Halt (1)
Open Loop Halt	Open Loop Halt (2)
Direct Output Halt	Direct Output Halt (3)

Auto Stop
Auto Stops automatically trigger a halt when an Error Bit is set. The Auto Stops can be configured to trigger any level of halt, or Status Only, for each individual Error bit. See theAuto Stops topic for details.
Fault Controller (8) Command
The Fault Controller (8) command will halt all the axes.