1.2 2572 Functions
Server Mode
In Server Mode, the module responds to PLC commands embedded in the TCP/IP packet. The initiating device (usually a computer or a 2572 operating in client mode) encapsulates the PLC command in the TCP/IP protocol and transmits it to the IP address of the 2572. The 2572 retrieves the command from TCP/IP and formats a corresponding request to the PLC processor. When the 2572 receives the response from the PLC processor, it encapsulates the response in the TCP/IP protocol and transmits it back to the IP address which sent the initial command.
No PLC programming is required to support server mode. However, the initiating device must encapsulate the proper command in the TCP/IP protocol and must properly process PLC responses which the 2572 embeds in TCP/IP. Many operating systems contain support for TCP/IP. Unix contains native TCP/IP support; IBM OS/2 and Microsoft Windows provide optional TCP/IP support. MS DOS does not directly support TCP/IP, but several companies offer DOS TCP/IP drivers.
Client Mode
In Client Mode, the 2572 can initiate a TCP/IP message. PLC logic is used to tell the 2572 what to send, where to send it, and when to send it. Using 2572 Client Mode, the local PLC can read and write memory in other remote PLCs or it can send messages to supervisory computers based on events detected by the PLC (alarm detection, data logging, etc.). Since a 2572 can operate as both a server and a client, multiple PLCs (each with a 2572), can participate in peer to peer communications.
Serial Redirect
Serial Redirect is a very powerful feature which routes data received at a serial port on the module to another node on the network. Once the serial port has been configured for the type of service and a destination address has been established, the 2572 will encapsulate the serial port data in TCP/IP and send it to the destination. Replies from the destination address will be routed back to the serial port. Using Serial Redirect, devices which normally communicate with the programming port of the PLC can access remote PLCs. For example, a PC running TISOFT could download programs to other PLCs on the network.
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CTI 2572 Technical Overview Manual