GFK-2224Q January 2017 135Chapter 8 Modbus/TCP ServerThis section describes the implementation of the Modbus/TCP Server feature for the PACSystems family ofproducts.▪ Modbus/TCP Server▪ Reference Mapping▪ Modbus Function Codes8.1 Modbus/TCP ServerThe PACSystems products listed below support Modbus/TCP Server functionality:▪ CPU010 and CPU020 with primary firmware version 3.0 or later.▪ CRE020 with Ethernet firmware version 3.0 or later.▪ RX7i: IC698ETM001 and RX3i IC695ETM001 with firmware version 3.0 or later.▪ CRE305 and CRE310 with primary firmware version 7.30 or later▪ Available on CPE330 Release 8.50.▪ Available on all versions of CPE400.Modbus/TCP Server ConnectionsThe Modbus/TCP Server supports up to 16 simultaneous connections. These connections are not shared withany other applications. Other TCP-based application protocols such as SRTP Server use a different set of TCPconnections.Modbus Conformance ClassesPACSystems 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 inconformance with Conformance Test Policy Version 2.1.Server Protocol ServicesThe Modbus/TCP Server responds to incoming Request Connection, Terminate Connection and Request Servicemessages. The client with which the server is interacting should wait for the server’s response before issuingthe 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 theconnection is terminated.Station Manager SupportThe Modbus/TCP Server supports the standard Station Manager commands: STAT, TALLY, and TRACE, plus theModbus/TCP server-specific KILLMS command. The Modbus/TCP Server task letter is “o”.8.2 Reference MappingThe Modbus protocol’s reference table definition is different from the internal structure of the PACSystemsreference tables. Modbus refers to Holding Register, Input Register, Input Discrete and Coil tables; PACSystemsuses Discrete Input (%I), Discrete Output (%Q), Analog Input (%AI), Register (%R), and Word (%W) reference
