Modbus

Basic Modbus Implementation for Centrilift Products
Version 1.6 – Dec 7, 2001

1.0 Introduction:
The following document will outline a short list of the Modbus data addresses most often used when integrating Centrilift Control Technologies products into SCADA systems. This document is not intended to describe every register available to the SCADA integrator. Each of the products discussed hasnumerous other registers available for use. The user should consult the product operator’s manual for the complete list of available registers, should he/she require more than a basic SCADA implementation.

1.1 Fixed Speed Control Products
Centrilift manufactures two fixed speed control and protection products. The Vortex VMC-100 Motor Controller is the original motor protection relay with avery large installed base around the world. More recently the Vortex GCS Motor Controller has been introduced. The Vortex GCS has all the basic protection and control features of the VMC-100, but also adds historical logging, diagnostics, datalogging capabilities, a graphic interface, and many other advanced operational features. The basic parameters of either device that are most often used inSCADA systems are grouped below according to the type of data (input/output, status/register) Input Registers (Measured or calculated values): 3 phase motor amps (A, B, C) 3 phase line voltage (AB, BC, CA) 2 analog inputs Input Current Unbalance (%) Input Voltage Unbalance (%) Cause of Last Shutdown Input Status (State of digital or status Inputs): Run status (status of Motor Contactor) 2 Digital /Status Inputs Output Registers (Parameters that can be read or written): Underload Setpoint Overload Setpoint Current Unbalance Setpoint Undervoltage Setpoint Overvoltage Setpoint Voltage Unbalance Setpoint Output Coils (Read/Write Digital Outputs, controlled as a relay coil): Start/Stop

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1.2 Variable Speed Control Products
There are also two product lines that are manufactured byCentrilift in the Variable Speed Drive category. The ICS Electrospeed VSD, with the addition of an Integrated Communication Module (ICM) is fully Modbus capable. The new GCS Electrospeed VSD has built-in communication functionality, and offers the same advanced features as the Vortex GCS products. As with the fixed speed products, the variable speed products have common monitoring and control functions,though the modbus addressing between the product lines differs. The basic parameters for operation and monitoring are grouped below. Input Registers (Measured or calculated values): Present Running Frequency 3 phase output amps Output Voltage Analog inputs Last Shutdown Cause Input Status (State of digital or status inputs): Run Status (Run, Stop, Accel, Decel, Ilimit, Sync) Digital / Status inputsOutput Registers (parameters which can be read or written): Set Frequency – desired output frequency Underload Setpoint Overload Setpoint Volts @ 60 Hz Current Limit (ILimit) Setpoint Acceleration (Accel) Time Deceleration (Decel) Time High Speed Clamp Low Speed Clamp Output Status(Read/Write Digital Outputs, controlled as a relay coil): Start/Stop

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1.3 General Notes
All registeraddresses are decimal unless specified as hexadecimal with an ‘h’ suffix. Modbus Addressing ( excerpt from Modbus protocol spec) Messages with function Codes 1-6, 15 & 16 indicate the register location(s) in the device as follows: Function Codes 1, 5, &15 refer to Coils (0xxxx), Function Code 2 refers to Inputs (1xxxx), Function Code 4 refers to Input Registers (3XXXX), and Function Codes 3, 6, and 16refer to Holding Registers (4XXXX). All address references in the Modbus messages are numbered relative to zero. For example, the first holding register in a given device might be 40001, and would be referenced as 0000. Similarly, a coil address of 00127 would be 0126(decimal) = 007Eh. Register values are unsigned integers in the range of 0 to 65535. This causes problems with some operating...