Module identity and key constraints
The Siemens 6ES7138-4DF01-0AB0 is a 15 mm-wide electronics module for the ET 200S distributed I/O system, handling one serial interface channel over RS232, RS422, or RS485. It runs ASCII and 3964(R) protocols up to 115.2 kbit/s, half- or full-duplex depending on the physical layer. Powered from the 24 V DC backplane supply — reverse polarity protected, draws up to 120 mA from L+ and 10 mA from the backplane bus. Typical power loss is 1.2 W.
Integration note — width and wiring
At 15 mm width it fits into one ET 200S terminal module slot. The RS232 interface brings out eight signals (TxD, RxD, RTS, CTS, DTR, DSR, DCD, PE); the other interfaces use two-wire (A/B) lines with GND. Cable length reaches 1 200 m on those interfaces. Ambient range is 0 to 60 °C.