Chapter 8 Modbus/Tcp Server; Modbus/Tcp Server; Modbus/Tcp Server Connections; Modbus Conformance Classes - GE RX3i User Manual

Chapter 8 Modbus/TCP Server

This section describes the implementation of the Modbus/TCP Server feature for the PACSystems family of
products.
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Modbus/TCP Server

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Reference Mapping

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Modbus Function Codes
Modbus/TCP Server
8.1
The PACSystems products listed below support Modbus/TCP Server functionality:
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CPU010 and CPU020 with primary firmware version 3.0 or later.
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CRE020 with Ethernet firmware version 3.0 or later.
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RX7i: IC698ETM001 and RX3i IC695ETM001 with firmware version 3.0 or later.
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CRE305 and CRE310 with primary firmware version 7.30 or later
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Available on CPE330 Release 8.50.
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Available on all versions of CPE400.

Modbus/TCP Server Connections

The Modbus/TCP Server supports up to 16 simultaneous connections. These connections are not shared with
any other applications. Other TCP-based application protocols such as SRTP Server use a different set of TCP
connections.

Modbus Conformance Classes

PACSystems Modbus/TCP Server supports Modbus Conformance classes 0, 1, and 2.
The RX3i Ethernet module has been certified by the Modbus/TCP Conformance Test Laboratory to be in
conformance with Conformance Test Policy Version 2.1.

Server Protocol Services

The Modbus/TCP Server responds to incoming Request Connection, Terminate Connection and Request Service
messages. The client with which the server is interacting should wait for the server's response before issuing
the next Request Service, otherwise requests could be lost.
There is no inactivity timeout in the server. If a client opens a connection, that connection stays open until the
connection is terminated.

Station Manager Support

The Modbus/TCP Server supports the standard Station Manager commands: STAT, TALLY, and TRACE, plus the
Modbus/TCP server-specific KILLMS command. The Modbus/TCP Server task letter is "o".
8.2 Reference Mapping
The Modbus protocol's reference table definition is different from the internal structure of the PACSystems
reference tables. Modbus refers to Holding Register, Input Register, Input Discrete and Coil tables; PACSystems
uses Discrete Input (%I), Discrete Output (%Q), Analog Input (%AI), Register (%R), and Word (%W) reference
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