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Introduction
2
Introduction
This reference guide assumes that the reader has a working knowledge of the Modbus
RTU Protocol and familiarity with the programming and operation of motion control
equipment. This guide is intended as a reference only.
2.1
Overview
Modbus is an internationally accepted asynchronous serial protocol designed for
commercial and industrial automation applications. The Modbus RTU architecture is
based upon a PLC to device communication structure and, as such is Master-Slave
in orientation. The SMV drive, in this case, always acts as the slave in this network,
responding to commands and requests from the Master.
While the Modbus RTU protocol does not specify the physical layer, the ESVZAR0
module uses the RS-485 physical interface which is quite common and well suited for the
industrial environment. The ESVZAR0 module provides both galvanic and optical isolation
of this physical interface.
2.2
SMVector Modbus RTU Implementation Specifications
Typical communications between master and slave would be:
• Write commands from Master
-
Run command
-
Frequency Reference
-
Modification of Drive operating parameters
• Requests from Master
-
Reporting of drive status
-
Fault status (and fault history)
The SMVector drive most nearly conforms to the Modicon
®
Micro 84 in capabilities. This
may be of importance when configuring networks for DDE Servers.
The following table identifies the Modbus serial communication specifications. If
the specification is fixed (non-adjustable) the value is shown under “Range”, if the
specification is selectable, the table identifies the Parameter and available range of
selections.
Description
Type
Range
Baud Rate
Selectable
P411
(2400, 4800, 9600, 19200, 38400, 57600, or 115200 bps)
Data Bits
Fixed
8
Parity / Stop Bits
Selectable
P412
(None/1, None/2, Even/1, Odd/1)
Network Address
Selectable
P410
(1 - 247)
