GE AF-600 FP Design Manual page 109

6.2.1 Drive with Modbus RTU
The Drive protocol provides access to the Control Word and Bus Reference of the frequency converter.
The Control Word allows the Modbus master to control several important functions of the frequency converter:
• Start
• Stop of the frequency converter in various ways:
Coast stop
Quick stop
DC Brake stop
Normal (ramp) stop
• Reset after a fault trip
• Run at a variety of preset speeds
• Run in reverse
• Change of the active set-up
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• Control of the two relays built into the frequency converter
The Bus Reference is commonly used for speed control. It is also possible to access the parameters, read their values, and where possible, write values to them.
This permits a range of control options, including controlling the setpoint of the frequency converter when its internal PID controller is used.
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AF-600 FP Design Guide