GFK-2224Q January 2017 139Chapter 9 Modbus/TCP ClientThis chapter explains how to program communications over the Ethernet network using Modbus/TCP Channelcommands. This chapter applies only to PLCs being used as client PLCs to initiate Modbus/TCPcommunications.▪ The Communications Request▪ The COMMREQ Function Block and Command Block▪ Modbus/TCP Channel Commands▪ Status Data▪ Controlling Communications in the Ladder Program▪ Differences between Series 90 and PACSystems Modbus/TCP Channels9.1 The Communications Request“Communications Request” is a term used to describe all the user elements required for correctly initiatingChannel commands in the client. No programming of Communications Requests is required for devices actingas servers
