Motion Direct Drive Off (MDF)
This information applies to the
CompactLogix
5370, ControlLogix
5570, Compact GuardLogix
5370, GuardLogix
5570, and ControlLogix
5580 controllers.Use the Motion Direct Drive Off (MDF) instruction to deactivate the servo drive and to set the servo output voltage to the output offset voltage. The output offset voltage is the output voltage that generates zero or minimal drive motion. You can specify this value during axis configuration.
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 |
Available Languages
Ladder Diagram
Function Block
This instruction is not available in function block.
Structured Text
MDF(Axis,MotionControl);
Operands
Ladder Diagram and Structured Text
Operand | Type ControlLoigx 5570, ControlLogix 5580, GuardLogix 5570 and GuardLogix 5580 | Format | Description |
|---|---|---|---|
Axis | AXIS_SERVO | Tag | Motion Axis of data type AXIS_SERVO only. 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 | 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 when the rung makes a false-to-true transition and remains set until the servo message transaction is completed and the rung goes false. |
.DN (Done) Bit 29 | It is set when the axis' drive signals have been successfully disabled and the drive enable status bit is cleared. |
.ER (Done) Bit 28 | It is set to indicate that the instruction detected an error, such as if you specified an unconfigured axis. |
Description
For motion module’s with an external servo drive interface, the MDF instruction directly disables the motion module Drive Enable output of the specified physical axis and also zeroes the modules' servo output to the external drive by applying the configured Output Offset value.
The MDF instruction is used to stop motion initiated by a preceding Motion
Direct Drive
On (MDO) instruction and transition the axis from the Direct Drive
Control state back to the Axis Ready state.To successfully execute an MDF instruction, the targeted axis must be configured as a Servo axis. Otherwise, the instruction errors.
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.
This is a transitional instruction:
- In relay ladder, toggle the EanbleIn false to true each time the instruction should execute.
- In structured text, condition the instruction so that it only executes on a transition.
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 the 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, and .ER are cleared to false. |
Rung-condition-in is false | The .EN bit is cleared to false if the .DN or .ER bit is true. |
Rung-condition-in is true | The .EN bit is set to true and the instruction executes. If the EN bit is set to false, then there is no action taken, |
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. |
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.MDF Changes to Single Axis Status Bits
Axis Status Bits
Bit Name | State | Meaning |
|---|---|---|
DriveEnableStatus | TRUE | Axis is in Axis Ready state with the Drive Enable output now active. |
Examples
Relay Diagram
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