Product Description

The MS/TP (Master Slave/Token-Passing) protocol is meant for connecting BACnet devices in serial networks using the standard EIA-485. Devices such as actuators, variable frequency drives, pumps, room-operating units, sensors, chillers, and compact air-conditioning units feature MS/TP protocol. The EL6861 is a serial interface by Beckhoff that connects BACnet MS/TP devices by means of RS485 interface. The RS485 interface generates electrically isolated signals, thereby guaranteeing high interference immunity. The EL6861 serial interface is capable of connecting up to 32 BACnet devices. If ultra-low power transceivers are used, it can accommodate up to 64 devices.

Beckhoff’s EL6861 features 3 LEDs to indicate the status of the serial network. The RUN LED is located at the top to indicate the terminal’s present state, and two other LEDs give status-indications. The EL6861 serial interface features a 9-point D-sub female socket right underneath the LEDs. The serial interface weighs approximately 70 grams and has dimensions of 26mm x 100 mm x 52 mm (W x H x D). It should be mounted on a 35 mm mounting rail as per EN60715.

The MS/TP protocol uses NRZ for different interface settings; 1 Startbit, 8 Databits, No Parity, 1 Stopbit, short form: 8,N,1. The EL6861 BACnet-MS/TP serial interface supports varying data transfer rates; 9600 (default), 19200, 38400, 57600, 76800 and 115200 baud. The EL6861 features 2 layers; the EIA-485 layer which is available for MS/TP networks, and a Logic ISO/OSI layer which is meant for BACnet enabled devices.