Q: Is it equivalent to the role of an MPI cable?
A: This question often arises when people confuse the dedicated network connector with the Siemens communication protocol. They are two distinct concepts. The DP bus connector with a programming port is simply a type of network connector, while MPI refers to a specific communication protocol. In most PLC applications, the MPI port on the PLC is typically connected using a DP bus connector for tasks such as uploading, downloading, or monitoring the program.
It's important to note that the physical layer for PPI, MPI, and PROFIBUS-DP communication in Siemens PLCs all use RS-485 technology. This means the same type of communication cable and special connectors can be used across these protocols. Siemens provides two types of network connectors: a standard one and a programming port connector. The latter allows a programming device or PC to connect to the network without disrupting existing communications.
MPI is a proprietary communication protocol developed by Siemens specifically for PLCs. As a result, Siemens PLCs come equipped with an MPI interface. When a PG/PC connects via the MPI interface, it can access all intelligent modules connected to the hardware stations on the network.
On the other hand, the DP bus connector with a programming port is just a physical connector that includes a programming port. It functions as a standard network connector between DP slaves but is more commonly used for connecting to the MPI port on the PLC for uploading, downloading, or monitoring purposes.
If you open the hardware configuration interface, double-click the corresponding CPU, and go to its properties, you'll see a communication sub-menu. The PLC operating system automatically reserves a connection resource for the PG or PC, allowing it to connect at any time. Importantly, the MPI interface does not interfere with normal network communication, making it a reliable tool for system diagnostics and maintenance.
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