144 Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018
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-condition-in 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.
Runtime Error Condition
For the Master Driven Speed Control (MDSC) function, an error will occur at
runtime if you attempt to change the mode of the system from Master Driven to
Time Driven or from Time Driven to Master Driven.
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.
Extended Error codes for the Parameter Out of Range (13) error code lists a
number that refers to the number of the operand as they are listed in the faceplate
from top to bottom with the first operand being counted as zero. Therefore for
the MCD instruction, an extended error code of 4 would refer to the Speed
operand’s value. You would then have to check your value with the accepted range
of values for the instruction.
For the Error Code 54 – Maximum Deceleration Value is Zero, if the Extended
Error returns a positive number (0-n) it is referring to the offending axis in the
coordinate system. Go to the Coordinate System Properties General Tab and look
under the Brackets ([ ])column of the Axis Grid to determine which axis has a
Maximum Deceleration value of 0. Click on the ellipsis button next to the
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