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You should now be able to see all connected stacks in the Brick Viewer. The Master Brick has to be restarted to apply the new configuration. A Modbus RS485 connects a Master device to one or more Slave devices. Not more than one breakout board is required per RS485 line. The RS485 data transmission standard requires that each network node be linked via a single transmission line terminated at each end in its characteristic impedance. And the results before was a degraded signal that the devices near the end would interpret the signal incorrectly. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds. The standard is jointly published by the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). The foreword to the standard references The Telecommunications Systems Bulletin TSB-89 which contains application guidelines, including data signaling rate vs. How come reading data from the RS485 adapter never succeeds?

With this boards, a CBL03 lines with RJ11 connectors can branch out to support an RS485 line consisting of three discrete wires. Extending a RS232 line is done by converting the RS232 signal into RS422 and then back to RS232 at the remote end. At the transmitter end the voltage difference should not be less than 1.5 Vdc and not exceed 5 Vdc. This cable provides a USB type A connector for the PC end and an RJ11 connector for the meter end. The cable to be used is a shielded twisted pair (telephone type). Common telephone cable is often twisted. Note that these cables are different from4-wire telephone cables or crossover cables. Both protocols (or communication languages) are built into the instrument’s firmware and are user selectable. Some of these converters can convert from RS232 to both RS485 and RS422 however many standard models only has one of the protocols. For example, Belden 3105A cable can be specified, but different types of cable with equivalent characteristics can be used.

RS485, also known as TIA/EIA-485 is a standard serial communications protocol defining the electrical characteristics of a serial converter, drivers and receivers for use in balanced RS485 digital multipoint systems. The symmetrical pin layout of the RJ11 sockets on the Unitronics PLCs allows an easy way of interconnecting the PLCs with both RS232 and RS485 communications. Usually a RS232 - RS485 converter is the preferred way to establish multi-point networks when working with RS232 devices. The RS485 interface allows the creation of multi-point networks. The advantage of the RS485 protocol is that this it can transfer data over longer distances, up to 4000 feet, and have up to 32 nodes per single network, and it can be used for multi-point networks where multiple serial devices are setup in a bus network. When in full RS232 mode, the six available pins are assigned to the most used RS232 signals. The central four pins remain their original RS232 functionality. When the DSR and DTR signals are not used, the two pins can be used for simultaneous RS485 communication. In RS232 mode all pins are used for RS232 signals. Daisychaining the network is prefered above a star topology, although both are allowed.

This allowed users in manufacturing facilities to connect larger applications and whole machines with one protocol. Both boards support the Modbus protocol and Laurel’s Custom ASCII protocol, as well as half-duplex or full-duplex RS485 communications. Laureate meter and LT series transmitters support the Modbus RTU protocol and Laurel’s simpler ASCII character based Custom ASCII protocol. Set the PC to N81 for the Custom ASCII protocol, or to N82 or E81 for the Modbus RTU protocol. With Modbus RTU, sending and receiving are never simultaneous, so half duplex is as fast as full duplex. The two jacks are wired in parallel by circuit traces on the circuit board. The two jacks are for RS485 cable in and RS485 cable out. Laureate RS485 boards are available in versions with dual RJ11 jacks (ordering option 2, board P/N L485) and with dual RJ485 jacks (ordering option 4, board P/N LMOD). These cables allow the dual RJ11 jacks of the RS485 option board of Laureate meters (digital interface ordering option 2) to be daisy chained and to be addressed digitally with no need for a hub.