Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 97
Master Driven Speed Control (MDSC) and the MAH Instruction
When either an MDAC or MDCC is active:
• If a MAH is executed (goes IP) on a Master axis and the Master axis is not
moving, the MDAC or MDCC remains active. If MDAC or MDCC is
active while the MAH is executed (goes IP), the slave moves.
• If an MAH is executed (goes IP) on a Master axis and the Master axis is
moving, the MAH will error. The MDAC or MDCC state remains
unchanged.
• If an MAH is executed (goes IP) on a Slave axis and the Slave axis is not
moving, the MDAC or MDCC is canceled.
• If an MAH is executed (goes IP) on a Slave axis while it is moving in MDSC
Driven or Time Driven modes, the MAH will error. The state of MDAC or
MDCC remains unchanged.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. 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 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 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 Ladder Diagram table.
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