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Because typical computer interfacing distances are very short compared to the 4000-foot limit of RS485, the type of cable used is not overly important. The main advantages of RS422, when compared to RS232, arise from RS422 using twisted-pair, balanced transmission lines. When using RS232, the serial connections between the computer and SMINI are made using the 3-pin header along the top right edge of the card. Additionally, connections between nodes should be contiguous from the computer to the first node, then on to the next and then the next. Each additional node is simply daisy-chained, with the same 4-wire cable running from the computer to the first node, on to the second, RS485 standard to the third and so on up to a possible total of 16 nodes. This setup facilitates easy daisy-chaining from node to node. And, because we are using the more advanced RS485 ICs, we expand our maximum node capability from 16 to 128. Because of this doubling up of the number of RS485 transceiver ICs and the corresponding use of 4-wires, this arrangement is typically referred to throughout the commercial and industrial world as a "Full Duplex" implementation of RS485. For more reliable, error-free transmission over long distances, you should use RS485.

Since data rates on a PC serial port can vary from 300 baud (26mS for 8-bits) up to over 100k baud (0.08mS for 8-bits), the timer will have to either be limited in the baud rates that it can work with, or keep control of the RS-485 network for much longer than it needs. To achieve each of the other 4 baud rates, the corresponding segment is set to the on, or up, position. RC4 used as input to read in the SMINI address DIP switch segment A6. If more than one segment happens to be turned on, the software within the SMINI defaults to using the baud rate corresponding to the highest switch segment with an "on" setting. With the ground potential problem reduced, the RS422 can send its Mark and Space signals closer together to operate reliably at higher baud rates and over greater distances. It is known for being able to be used effectively over long distances and in electrically noisy environments. The RS485 and RS232 serial communication protocols have been in use for over 50 years and are still widely used throughout business and industry.

None of these protocols are part of the RS-485 standard, and implementation is up to the engineer writing the software. Such installations are not standard, but they do work. Such cross-coupling effects become especially prevalent where RS485 cable runs are long and in close parallel proximity to DCC or Railcommand track wiring. This is significant because a serial interface transmits data sequentially, one bit after another, as opposed to a parallel interface, which for example might transmit one byte (eight bits) at a time. The 4-wire design, as implemented by the C/MRI, takes advantage of both worlds, RS422 and RS485, by dedicating one set of the more advanced RS485 transceivers to sending data from the PC and a second set for handling data being received by the PC. To be on the conservative side, it is always best to use dual twisted pair shielded transmission cable for RS485. Proper cable termination, a topic covered near the end of this chapter becomes increasingly important as cable length is increased. This article aims to explore this topic and assist you in selecting the flow meter that best suits your needs. Intertec best electric heaters are for sale for T3, T4 and as well T6 high temperatures modules, minimizing heater yard to assist you to 160, 40 or even 50C correspondingly.

Two-way resistor termination: Works best on a linear bus, with transmitters anywhere along the bus. RS-485 signals transmit on a serial bus, meaning all senders (masters or managers) will be detected by all receivers. When the input is low or 0, the non-inverting output will go low. When an SMINI is talking to the PC, the SMINI card’s U7 transmit IC is in effect operating in a low impedance state driving the two bus lines with ‘1s’ and ‘0s’. Whereas RS232 can support communication between only two devices, an RS422 port can be connected with up to 16 devices, or nodes. However, with real-time applications such as the C/MRI the overall system performance can be degraded when using USB. That is suitable for many applications such as connecting a printer, modem or a single SMINI or SUSIC to your computer. In applications where the bit time closely aligns with the cable loop time, termination is vital to minimize reflections. Matching the cabling’s characteristic impedance to the termination network allows the receiver to maximize signal power detection.