Allen-Bradley Micro800 General Instructions Manual page 434

Chapter 17
Motion control instructions
Rule applies to
Output Active
Enable and Valid status
Output error handling
Naming conventions ENUM types
434
Rule
The Active output is required on buffered function blocks, and is set at the moment the function block takes control of the
motion of the according axis.
For unbuffered mode, the Active and Busy outputs can have the same value.
The Enable input is coupled to a Valid output. Enable is level sensitive, and Valid shows that a valid set of outputs is available at
the function block.
The Valid output is TRUE as long as a valid output value is available and the Enable input is TRUE. The relevant output value can
be refreshed as long as the input Enable is TRUE.
If there is a function block error, the output is not valid (Valid set to FALSE). When the error condition disappears, the values
reappear and Valid output is set again.
Outputs used to define errors
All blocks have the following two outputs that are used for errors that occur during execution:
• Error – Rising edge of "Error" informs that an error occurred during the execution of the function block.
• ErrorID – Error number.
Note: Done and InVelocity outputs are used for successful completion so they are logically exclusive to Error.
Instance errors do not always result in an axis error (bringing the axis to ErrorStop).
How the error outputs are reset
• Error outputs of the relevant function blocks are reset with tje falling edge of Execute and Enable.
• The error outputs of a function block with Enable can be reset during operation without having to reset Enable.
Types of errors
• Function blocks logics (for example, parameters out of range, state machine violation attempted, and so on)
• HW Limit or SW Limit
• Mechanism/Motor
• Drive
Due to the naming constraints in the IEC standard on the uniqueness of variable names, the 'mc' reference to the PLCopen
Motion Control namespace is used for the ENUMs.
In this way we avoid the conflict that using the ENUM types 'positive' and 'negative' for instance with variables with these
names throughout the rest of the project since they are called mcPositive and mcNegative respectively.
Rockwell Automation Publication 2080-RM001D-EN-E - February 2015