Siemens 6ES5521-8MA22 Serial Communication Module

Siemens 6ES5521-8MA22 CP 521 SI Communications Processor is a serial-interface module for SIMATIC S5 systems. It is designed for use in S5-90U, S5-95U, S5-100U, and ET 200U configurations, including ET 200U distributed I/O stations, and features its own central processor to handle serial communications. The module provides a single RS-232/V.24 serial interface (V.24/TTY) with an optional 20 mA current-loop path, and the interface is designed for asynchronous data exchange with external devices. It supports 10-bit and 11-bit character framing and lists 110 Bd as a transfer rate option in its technical data. The CP521 SI is specified as an isolated serial interface, helping separate the CP from the host bus. In addition, MODBUS compatibility can be achieved via an optional System Submodule, expanding interoperability with third-party devices beyond the S5 protocol.