Siemens CP340 RS422/485 Communication Processor for SIMATIC S7-300 (order number 6ES7-340-1CH00-0AE0) provides a dedicated serial link on the S7-300 PLC backplane for point-to-point RS-422/RS-485 communication. The module uses a 15-pin Sub-D front connector and supports RS-422 in full-duplex (4-wire) or RS-485 in half-duplex (2-wire) configurations. Designed to connect the S7-300 to other PLCs or serial devices such as printers or terminals, it extends the PLC's reach over a serial network. This CP340 variant is explicitly described as CP 340–RS 422/485 in Siemens documentation and catalog listings.
