P94MOD01B
1.2 Reference Documents
•
Modbus Application Protocol Specification V1.1
To view this specification, visit: http://www.modbus.org/tech.php
or: http://www.modbus-ida.org/specs.php
•
Modbus Over Serial Line Specification & Implementation Guide V1.0.
Refer to: http://www.modbus.org/
•
PositionServo Programming Manual: PM94P01
Refer to: http://www.actech.com
NOTE:
The complete list of variables can be found in Appendix A of the PositionServo
Programming Manual (PM94P01).
2.
Introduction
This reference guide assumes that the reader has a working knowledge of Modbus RTU or Modbus TCP/IP
Protocol and familiarity with the programming and operation of motion control equipment. This guide is intended
as a reference only. The PositionServo drive supports both Modbus TCP/IP and Modbus RTU communication
protocols. Modbus TCP/IP communications can be established via the PositionServo drive’s Ethernet port.
When using the RS485 option module (P/N E94ZARS41), Modbus RTU is the standard communication protocol.
Refer to Section 3 for installation of the RS485 option module.
2.1 Modbus Overview
Modbus is an internationally accepted asynchronous serial protocol designed for commercial and industrial
automation applications. The Modbus RTU architecture is based upon a Master-Slave orientation. In Modbus
RTU, the PositionServo drive always acts as the slave, responding to reads and writes from the Master. In
Modbus TCP/IP, the PositionServo drive can act as the Master or a slave. While the Modbus RTU protocol does
not specify the physical layer, the E94ZARS41 module uses a 2-wire RS-485 physical interface which is quite
common and well suited for the industrial environment. The E94ZARS41 module provides both galvanic and
optical isolation of the physical interface.
2.2 Ethernet TCP/IP Modbus Configuration
The PositionServo Drive is a standard ModbusTCP slave device and its IP address, subnet mask and default
gateway can be configured using MotionView software. It supports up to two (2) simultaneous connections
on the standard Modbus TCP port 502. On open connections with no activity for more then 75 seconds, the
PositionServo Drive sends a TCP keep-alive message every 75 seconds to check the connection status.
