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The adapter includes a 3 foot 'type A' cable connection that plugs into any PC or MAC USB port. Removing the WiFi adapter and connecting directly to the inverter's COM port resulted in no data again so we knew that there was something on the WiFi adapter enabling the data from the inverter. For communications, many of their products are equipped with an RS232 or RS485 serial port. These pins are normally used for the DTR, data terminal ready and DSR, data set ready signals. A symmetrical pin-layout allows two DTEs, data terminal equipment, to be connected directly without use of a modem or other DCE, data communication equipment. The RS485 system used for Modbus communication provides a main cable (Bus or backbone), to which all the devices have to be connected with branches (also known as stubs) that are as short as possible. The main difference is, that pin 1 and 6 on the RJ11 socket of the MJ20-PRG module are used as power supply. Pin 1 and 6 however are reassigned to the A and B lines when the port is used in RS485 mode. This module is powered by the RS232 port from the connecting computer.

This MJ20-PRG module clicks in the PLC and provides one RJ11 socket for serial communications with a PC. The only way to add RS232 capabilities to the Jazz PLCs is by using the MJ20-PRG programming port add-on module. The USB to RS485 Converter is designed to make serial port expansion quick and simple. The Jazz PLC series from Unitronics are not standard equipped with a RJ11 connector for serial communications. To set up communications for your meter or counter, see the Serial Communications section of its user manual. When a single RS485 meter or counter is connected to a PC via a cable CBL06, set the PC to 9600 baud. See page 7 of the Laurel digital panel meter manual, page 7 of the Laurel counter manual, page 8 of the Laurel scale meter manual, or page 8 of the Custom ASCII protocol manual. 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. If multiple analog input meters or transmitters are digitally addressed in command mode on an RS485 line using the Modbus RTU protocol or the Custom ASCII protocol, the rate becomes about 2 readings per second.

Access control systems: Rs485 cables are mainly used to connect and transmit data between access control devices such as security gates, RFID cards, or time attendance machines and the control center. Industrial automation systems: In the industrial automation sector, rs485 signal cables play a vital role in connecting and remotely controlling motors. Alarm systems: Rs485 cables in alarm systems help transfer alarm signals and information from alarm devices to the control center. The A signals of all devices should be connected with each other and the same goes for the B signals. In order to avoid errors when many devices are connected, cables of the same colour should be used for all the connections to the terminals A and cables of the same colour should be used for all the connections to the terminals B of the various devices (e.g. white for A and blue for B). These signals are commonly called A and B in RS485 systems. For RS232 a crossover cable is used where pin 1 is connected with pin 6 at the other connector, pin 2 with pin 5, etc. This interconnects the transmit and receive signals of both PLCs, and also the handshaking signals DTR and DSR.

Normally pin 7 (RTS) and pin 4 (DTR) are used on the DB9 connector. Therefore the pin assignment is a little bit different from the default pin assignment on the RJ11 socket. The existence of an RS485 port on the socket makes it even a little bit more difficult. The RJ11 socket is interesting, because the manufacturer choose to have a symmetrical pin-layout, just as with the MMJ connector on DECconnect systems and the RJ45 jack in the Yost standard. Both will work with RJ11 connectors and CBL03 cables. With this boards, a CBL03 lines with RJ11 connectors can branch out to support an RS485 line consisting of three discrete wires. If not, check out our other blog post What is RS232. The two jacks are for RS485 cable in and RS485 cable out. 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. Video Sync Input and RS422 - Video multimedia applications require synchronization with the video when converting video to streaming format or in MIDI applications for sound synchronization.