The 6ES7138-4DF10-0AB0: This is a SIMATIC DP electronic module for ET 200S — one serial interface channel in a 15mm-wide slice that handles both USS and Modbus protocols. The interface is fully configurable for RS232, RS422, or RS485, so you can talk to drives on USS or legacy Modbus slaves without needing a separate gateway module. Rated for 24 VDC from the backplane, typical power loss is 1.2 W. Transmission rates from 110 bps up to 38.4 kbps, half-duplex. The module supports 7-byte send and receive blocks, with parity options (none, odd, even) and configurable character frames of 10 or 11 bits — USS demands 11-bit framing with 1 start/stop, and that's handled here.
Integration
Mounts directly on an ET 200S terminal module. The 15mm width is one of the slimmest slices in the range — critical when you're packing eight or more serial ports into a single head station. Depth is 52 mm, height 81 mm, so it clears most DIN-rail enclosures. RS232 cabling is good to 15 m shielded; RS422/485 runs out to 1 200 m shielded. The interface exposes all standard signals: TxD, RxD, RTS, CTS, DTR, DSR, DCD for RS232, and a differential pair for RS422/485. A galvanic isolation barrier exists between the serial port and the backplane supply.