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The GROUND line serves as a common voltage reference for the master and slave. Category 5 (Cat 5, Cat 5e, and Cat 6) cables are the most common Ethernet cables in use today. 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 maximum number of devices that can be connected to a main cable is 32, including the Master. Product offers a generic serial data/requests filtering feature, which allows you to configure filtering for different visualizers, create filtering schemes and quickly apply them to different visualizer windows.Additionally, you may change the appearance of visual elements for monitored packets in the data visualizers including MODBUS View, Request View (Serial, Bridge), Data View, PPP View. In order to increase the extent of the Modbus network, repeaters can be used; and signal amplifying and regenerating devices provided with two communication ports that transfer to each what they receive from the other.

Data Repeater sends all monitored data to a selected serial port (or two ports) and supports both active serial monitoring sessions and playback sessions. Reliable Supports high data transfer rates without affecting PC performance. Because all of the serial I/O routines on the QScreen Controller are revectorable, it is very easy to change the serial port in use without modifying any high level code. By polling the Port A pin or by setting up an interrupt service routine, you can configure the QScreen to ignore the SCK input when /SS is high and keep MISO in a high-impedance state so that it does not interfere with the SPI bus. Figure 1 shows an example of a correct Bus connection. Multiple receivers may be connected to such a network in a linear, multidrop bus. But there are some limitations to it as it cannot support multiple slaves and multiple masters and the maximum data frame is limited to 9 bits.

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). Up to 100 units may be connected to the same RS485 interface. In some countries, inserting two cables into the same screw terminal is permitted. If on the other hand each terminal can accept only a single cable, a proper branch must be created using three auxiliary terminals for each instrument to be connected. In this case it is possible to connect the main inlet and outlet terminal directly to the terminals of an instrument without creating a branch. Normally, this connection is made at one end of the main cable. End of line termination resistor (120 ohm 1/4 watt) to be installed at both ends of network. In order to avoid signal reflections, a 120 Ohm termination resistance must be fitted on each end of the main cable.

If the total length of the main cable is less than 50 m termination resistances can be avoided at the ends of the main cable. The termination also includes pull up and pull down resistors to establish bias for each data wire for the case when the lines are not being driven by any device. The shielding may be braided (be formed by a mesh of thin conducting wires) or be a foil (consisting of a sheet of metal wound around the conductors): the two types are equivalent. The twin consists of two conductors that are twisted together. In practice, Cat 5 cables have been used successfully in many installations, but there are some concerns. No I have not been able to test this using the Windows software. Previously we have also performed MAX485 communication with Arduino and also MAX485 Communication with Raspberry pi, you can also check them out if interested.

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