Title: 32 Pumper modbuss teknisk data.pdf.pdf
An APN connection (Access Point Name) is a wireless, "always on" connection that remains active as long as CIU 260 is within range of the service. With a data connection, it is possible to establish a wireless connection to the Internet and thus enable a remote connection to a SCADA system computer or another PC application.The APN connection itself takes care of the wireless data transfer via the cellular network. It plays the same role as Ethernet in a wired network. We will refer to an APN connection as a data connection, and it also makes use of the TCP/IP protocol, which enables easy integration with the Internet. The Modbus TCP protocol is used on the application layer communicating with a TCP port number (default 502). The difference when compared to the fieldbus protocol Modbus RTU is the exclusion of the 16-bit CRC checksum and the adding of a Modbus application program header as illustrated in fig. 23.Modbus RTU telegramSlave IDFunction code IDDataCRCModbus application program header