Specifications

Bulletin No. VVDED397044US R12/00 Section 2—Modbus Plus Overview
December 2000 ALTIVAR® 58 Registers and Data Exchange
© 1998–2000 Schneider Electric All Rights Reserved
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SECTION 2—MODBUS PLUS OVERVIEW
INTRODUCTION
The MODBUS
PLUS option card allows an ALTIVAR 58 (ATV58) drive
controller to function as a node on a MODBUS PLUS network. This
section explains how information is exchanged between the drive
controller registers and other nodes on the network. For a complete
description of MODBUS PLUS networks and protocol, or to reference
MODBUS PLUS terms and concepts, please refer to the following
Modicon documents:
•
MODBUS PLUS Network Planning & Installation Guide ,
890 USE 100 00
•
MODBUS Protocol Reference Guide , PI-MBUS-300
• Ladder Logic Block Library User Guide, 840 USE 10 100
ALTIVAR 58 REGISTERS AND DATA EXCHANGE
When an ATV58 drive controller is a node on a MODBUS PLUS network,
the data in its adjustment (read and write), command (read and write),
and display (read only) registers can be accessed by other devices on the
network. There are three ways to access the drive controller registers
with the MODBUS PLUS option card:
• Messaging
• Peer Cop
• Global Data
The following sections are an overview of MODBUS PLUS networks and
communication methods. For details on the drive controller registers and
their MODBUS PLUS addresses, refer to ATV58 Register Access Guide
for Communication Networks, VVDED397058US.
Messaging
Messaging is a method of peer-to-peer communication between
networked devices. It follows a query-response sequence. The initiating
device sends a query to a specific node and receives a response. When
messages are issued over a MODBUS PLUS network, the solicited node
must send an immediate acknowledgment. When the solicited node
holds the token, it may then send all requested data to the initiating node.