20 mA TTY interface — the serial link for legacy field devices
The 6ES7340-1BH00-0AE0: It supports ASCII and 3964(R) protocols — the ASCII channel tops out at 9.6 kbit/s, while 3964(R) can run at 19.2 kbit/s. The 1 024 byte buffer handles both ASCII and 3964(R) frames, enough for typical point-to-point telegrams from a scale or barcode reader. Maximum cable length is 1 000 m — 100 m for active TTY devices, 1 000 m for passive — giving flexibility for remote field devices in a plant.
Physical fit and backplane loading
The module occupies one S7-300 slot at 40 mm wide, 125 mm high, 120 mm deep — standard for the series. It draws 220 mA from the 5 V DC backplane bus, with a maximum power loss of 0.85 W — well within the S7-300 rack power budget. The configuration package ships on CD with the module, covering the CP 340 parameterisation in STEP 7.