6.2 Task Codes
As noted above the first word of the body of an NITP message contains a command. SIMATIC TI505 PLCs use a command structure known as task codes. Task codes are a set of numeric command codes which allow an external device to supervise and control the operation of the PLC. For example, using task codes a device can retrieve data from PLC memory.
Since NITP and Task Codes are the most common way of communicating with SIMATIC TI505 PLCs, the CTI 2572 TCP/IP implementation supports this interface. Thus, to communicate with the PLC via the 2572, all the application program has to do is encapsulate the NITP message format in the TCP/IP protocol. Similarly, a PLC with a 2572 operating in client mode can read and write memory in other PLCs using this method. In addition, it allows standard NITP devices attached to a 2572 serial port to communicate with remote PLCs.
Details of the command implementation are covered in the 2572 Installation and Operation Guide.
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CTI 2572 Technical Overview Manual
