Eight DIY RS485 Standard Suggestions You'll have Missed > 자유게시판

It defines a means of exchanging control signals and binary serialized data signals between data terminal equipment and a data communication channel in cases where interchange point. It defines a means of exchanging control signals and binary serialized data signals between data processing terminal equipment and data communication equipment, and is of particular importance when each is furnished by a different company. Just because a protocol is used with a particular implementation of RS-232 or RS-485, does not mean it is part of the standard. Meters with a thermocouple input and using the Modbus RTU protocol should be set to full duplex. RS485 will support 32 drivers and 32 receivers (we are talking about bi-directional - half duplex - multi-drop communications over a single or dual twisted pair cable !!). The meter, counter or timer should be programmed for full duplex operation, even if the RS485 board is jumpered for half duplex. RS-422 is similar (except they leave the hyphen out) Both standards have a section defining why you may want fail-safe operation, but neither discuss how to implement it. If multiple devices start to talk at the same time, the data may be corrupted.

This allows multiple instruments to be daisy-chaned using data cables (or patch cords) with RJ45 plugs; however, such data cables are not available from Laurel. However, four-wire networks may feature two twisted pair wires, where a master port with s transmitter is connected to slave receivers of one twisted pair and the slave transmitters are connected to the master receive of the second twisted-pair wire. It can be set to a command mode under control of an external master, or to a continuous streaming mode where data is output at specified intervals at rates up to 60 per second. Modbus RTU works in a master-slave (or query-response) mode, and its use requires an external Modbus master, which is typically a PC. Use of more than 31 Laurel RS485 Modbus boards requires repeaters for impedance reasons. The gateways boards all provide an RJ11 jack for connection to an RS585 bus with up to 31 Laureate instruments.

The LMOD or L485 boards can be configured for full-duplex or half-duplex operation using jumpers. Laurel's alternative L485 board with dual RJ11 jacks is supported by our RS485-to-USB converter cable (P/N CBL06) for data I/O and for programming by a PC running our Instrument Setup (IS) software. For new designs, use the functionally equivalent L485 board with dual RJ11 jacks. The Laureate P/N LMOD interface board with dual RJ45 jacks allows multiple Laureate meters, counters, timers and remote displays to be connected to the same RS485 line. Is port re-entrant. - State driven Xmodem and Ymodem on multiple ports simultaneously. When U1 needs to read data from an input port, U1 software switches the eight Port RD lines to be inputs. In the Widgetlords Electronics product lines that include a RS485 driver, the direction whether Receive or Transmit is controlled directly via a GPIO line. 20mA), RS485, and GPIO(Pulse). If you do, then U6 and U8 both fight to control the RX line resulting in faulty operation and possible IC damage. The transmission speed possible with an RS232 interface is 1Mb/s for a distance of up to 15 meters.

Devices using the RS232 protocol are limited to a distance of 15 meters between transmitter and receiver while still achieving the maximum data transmission rate. The RS485 standard is widely accepted in industrial automation along with the Modbus RTU protocol. The Modbus RTU protocol is an international standard and allows Laureates to share the same RS485 data lines with non-Laurel devices. The probes communicate using the standard Modbus RTU protocol. Two serial protocols are user-selectable for RS485: Modbus RTU and Custom ASCII. The /RE and DE lines are tied together, when set high the transceiver is in receive mode, when set low, the transceiver is in transmit mode. The display also indicates the status of the available set point relays. Laurel's Custom ASCII protocol is the simpler of the two protocols and uses ASCII strings. RS-232 does not define a protocol, but the protocol that is almost always transmitted on these connectors is asynchronous start-stop ASCII (data from a UART).