Specifications

Bulletin No. VVDED397044US R12/00 Section 1—Installation & Configuration

December 2000 Network Overview

NETWORK OVERVIEW

MODBUS PLUS is a Local Area Network system designed for industrial

control applications. Up to 32 node devices can connect directly to the

network bus cable over a length of up to 1,500 ft (450 m) including drop

lengths. Repeater devices are used to extend the cable distance to its

maximum of 6,000 ft (1,800 m) and the node count to a maximum of 64.

The MODBUS PLUS network provides host level, peer-to-peer

communication for networked PLCs. As a node on a MODBUS PLUS

network, the ATV58 drive controller can receive and respond to data

messages transmitted from a PLC and place information into the

network’s global database. Other nodes can access drive controllers on

the local network, or on remote networks through bridge devices. The

network also provides distributed input/output (DI/O) communications in

which PLCs communicate directly with input/output (I/O) subsystems.

The network must use a single-cable layout.

MODBUS devices or networks of MODBUS devices may join MODBUS

PLUS networks through bridge multiplexers. A multiplexer provides four

serial ports that are separately configurable to support MODBUS or

custom RS-232 / RS-485 devices. MODBUS devices can communicate

with MODBUS PLUS networked devices, as well as with devices at the

other serial ports.

1. For additional information, refer to NEMA ICS 1.1 (latest edition), “Safety Guidelines for

the Application, Installation, and Maintenance of Solid State Control” and to NEMA ICS7.1

(latest edition), “Safety Standards for Construction and Guide for Selection, Installation

and Operation of Adjustable-Speed Drive Systems.”

WARNING

LOSS OF CONTROL

• The designer of any control scheme must consider the potential

failure modes of control paths and, for certain critical control

functions, provide a means to achieve a safe state during and after a

path failure. Examples of critical control functions are emergency

stop and overtravel stop. Separate or redundant control paths must

be provided for critical control functions.

• System control paths may include communication links.

Consideration must be given to the implications of unanticipated

transmission delays or failures of the link.

Failure to follow this instruction can result in death, serious injury,

or equipment damage.