Motion Disarm Watch (MDW)
This information applies to the
CompactLogix
5370, ControlLogix
5570, Compact GuardLogix
5370, GuardLogix
5570, Compact GuardLogix
5380, CompactLogix
5380, CompactLogix
5480, ControlLogix
5580, and GuardLogix
5580 controllers. Controller differences are noted where applicable.Use the Motion Disarm Watch (MDW) instruction to disarm watch-position event-checking for an axis. This instruction has the effect of clearing both the Watch Event Status and Watch Armed Status bits in the axis data structure. Executing this instruction also clears the In Process bit associated with the controlling Motion Arm Watch (MAW) instruction.
Available Languages
Ladder Diagram
Use the Motion Disarm Watch (MDW) instruction to disarm watch-position event-checking for an axis. This instruction has the affect of clearing both the Watch Event Status and Watch Armed Status bits in the axis data structure. Executing this instruction also clears the In Process bit associated with the controlling Motion Arm Watch (MAW) instruction.
Architecture | Standard | Safety |
|---|---|---|
CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Yes | No |
Compact GuardLogix 5380, CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, and GuardLogix 5580 controllers | Yes | No |
Function Block
This instruction is not available in function block.
Structured Text
MDW(Axis,MotionControl);
Operands
Ladder Diagram and Structured Text
Operand | Type CompactLogix 5370, Compact GuardLogix 5370, Compact GuardLogix 5380, CompactLogix 5380, CompactLogix 5480 | Type ControlLogix 5570, GuardLogix 5570, ControlLogix 5580, and GuardLogix 5580 controllers | Format | Description |
Axis | AXIS_CIP_DRIVE | AXIS_CIP_DRIVE AXIS_SERVO AXIS_SERVO_DRIVE AXIS_GENERIC_DRIVE AXIS_GENERIC Tip: AXIS_GENERIC is supported by the ControlLogix 5570 and the GuardLogix 5570 controllers only. | Tag | Name of the axis on which to perform operation. For controllers that support the REF_TO motion data types, the supported axis operand type can be replaced by an equivalent REF_TO type. |
Motion Control | MOTION_INSTRUCTION | MOTION_INSTRUCTION | Tag | Structure used to access instruction status parameters. |
See
Structured Text Syntax
for more information on the syntax of expressions within structured text. MOTION_INSTRUCTION Structure
Mnemonic | Description |
.EN (Enable) Bit 31 | It is set to true when the rung makes a false-to-true transition and remains set to true until the servo message transaction is completed and the rung goes false. |
.DN (Done) Bit 29 | It is set to true when the axis watch event checking has been successfully disarmed. |
.ER (Error) Bit 28 | It is set to true to indicate that the instruction detected an error, such as if you specified an unconfigured axis. |
Description
The MDW instruction cancels watch position event checking set up by a previous Motion Arm Watch (MAW). The Disarm Watch Position instruction requires no parameters; simply enter or select the desired physical axis.
If the targeted axis does not appear in the list of available axes, the axis has not been configured for operation. Use the Tag Editor to create and configure a new axis.
To successfully execute a MDW instruction, the targeted axis must be configured as either a Servo or Feedback Only axis. Otherwise, the instruction errs.
IMPORTANT:
The instruction execution may take multiple scans to execute because it requires multiple coarse updates to complete the request. The Done (.DN) bit is not set immediately, but only after the request is completed.
In this transitional instruction, the relay ladder, toggle the Rung-condition-in from cleared to set each time the instruction should execute.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. A major fault can occur if an uninitialized reference or a reference of incorrect type is passed to the Axis Operand. See
Common Attributes
for operand-related faults.Execution
Ladder Diagram
Condition/State | Action Taken |
Prescan | The .EN, .DN, .ER, and .IP bits are cleared to false. |
Rung-condition-in is false | The .EN bit is cleared to false if either the .DN or .ER bit is true. |
Rung-condition-in is true | The .EN bit is set to true and the instruction executes. |
Postscan | N/A |
Structured Text
Condition/State | Action Taken |
Prescan | See Prescan in the Ladder Diagram table. |
Normal execution | See Rung-condition-in is false, followed by rung is true in the Ladder Diagram table. |
Postscan | See Postscan in the Ladder Diagram table. |
Error Codes
See
Motion Error Codes (.ERR)
for Motion Instructions.Extended Error Codes
Extended Error Codes provide additional instruction specific information for the Error Codes that are generic to many instructions. See
Motion Error Codes (.ERR)
for Motion Instructions.Status Bits
MDW Changes to Status Bits
Bit Name | State | Meaning |
WatchEventArmedStatus | FALSE | The axis is not looking for a watch position event. |
WatchEventStatus | FALSE | The previous watch event is cleared. |
Examples
When the input conditions are true, the controller disarms watch-position event-checking for axis1.
Ladder Diagram
Structured Text
MDW(Axis1,MDW_1);
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