What this CP 340 does in an S7-300 rack
The Siemens 6ES7340-1BH02-0AE0 is a CP 340 communications processor for the SIMATIC S7-300 platform, providing a single isolated 20 mA (TTY) interface for serial point-to-point links. It handles ASCII protocol up to 9.6 kbit/s and the 3964 (R) protocol up to 19.2 kbit/s, with a configurable data buffer of 1 024 bytes. Power is drawn from the backplane bus at 5 V DC, drawing up to 190 mA, with a typical power loss of 0.85 W.
Interface and protocol fit
The 20 mA (TTY) interface uses a 9-pin sub D socket and supports cable runs up to 1 000 m passive or 100 m active. Transmission rates are selectable from 2.4 kbit/s up to 19.2 kbit/s, with the printer driver mode capped at 9.6 kbit/s. Supported printers include HP-DeskJet, HP-LaserJet, and IBM-ProPrinter, plus user-defined types — useful for direct serial printing from the PLC without a PC intermediary.
Environmental and physical specs
The module measures 40 mm wide, 125 mm high, and 120 mm deep, fitting a single S7-300 slot width.