Motion Servo On (MSO)
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 Servo On (MSO) instruction to activate the drive amplifier for the specified axis and to activate the axis' servo control loop.
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
MSO(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_GENERIC AXIS_GENERIC_DRIVE AXIS_SERVO AXIS_SERVO_DRIVE 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 | tag | Structure used to access instruction status parameters. |
See
Structured Text Syntax
for more information on the syntax of expressions within structured text. 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’ servo action has been successfully enabled and the drive enable and servo active status bits have been set. |
.ER (Error) Bit 28 | It is set to indicate that the instruction detected an error, such as if you specified an unconfigured axis. |
Description
The MSO instruction directly activates the drive and enables the configured servo loops associated with a physical servo axis. It can be used anywhere in a program, but should not be used while the axis is moving. If this is attempted, the MSO instruction generates an Axis in Motion error.
The MSO instruction automatically enables the specified axis by activating the drive and by activating the associated servo loop. With a non-CIP axis, the resulting state of the axis is referred to as the Servo Control state. With a CIP axis, the resulting state of the axis is referred to as the Running state.
The most common use of this instruction is to activate the servo loop for the specified axis in its current position in preparation for commanding motion.
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 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, 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. |
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. These Extended Error codes help to pinpoint the problem when the MSO instruction receives a Servo Message Failure (12) error message. Extended Error Code (decimal) | Associated Error Code (decimal) | Meaning |
|---|---|---|
Object Mode conflict (12) | SERVO_MESSAGE_FAILURE (12) | Axis is shutdown. |
Process terminated on request (15) | SERVO_MESSAGE_FAILURE (12) | Enable input switch error. (SERCOS) |
Device in wrong state (16) | SERVO_MESSAGE_FAILURE (12) | Device State not correct for action. (SERCOS) |
MSO Changes to Status Bits
Axis Status Bit
Bit Name | State | Meaning |
|---|---|---|
ServoActionStatus | TRUE | Axis is in Servo Control state with the servo loop active. |
DriveEnableStatus | TRUE | The axis drive enable output is active. |
Motion Status Bits
None
Examples
Example 1
Ladder Diagram
Structured Text
MSO(myAxis, myMotionControl);
Example 2
Relay Ladder
Structured Text
MSO(Axis_01,MSO_1);
Provide Feedback