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The bus line has been interrupted (e.g.
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![rs485 modbus rtu rs485 modbus rtu](https://res.cloudinary.com/webstore/image/fetch/w_450,c_limit,c_fit,f_auto,e_trim/http%3A%2F%2Fluckyretail.com%2FUploadfile%2F202011%2F202106141%2F500113299A2%2F500113299A2.jpg)
This is the case under the following conditions: If the interface is not galvanically separated then the common connection must also be routed with it (Fig.: Image 1b). One cable pair should only ever be used here for A and B (Fig.: Image 1b). The communication between the sender and receiver takes place on a wired basis via shielded, twisted pair cable. The protocol used may be selected on an arbitrary basis, e.g. According to the OSI model (Open Systems Interconnection Reference Model)* only the "physical layer" and not the protocol is described. This information can either be found in the TSB89 "Application Guidelines for TIA / EIA-485-A" or in the application descriptions of the RS485 driver module manufacturers, such as Texas Instruments or Maxim. The standard only defines the electrical interface conditions of the sender and receiver, it does not say anything about the topology or the lines to be used.
RS485 MODBUS RTU UPDATE
The most recent update was in March 1998 and the standard was confirmed in 2003 without changes. The full name of the RS485 standard is TIA / EIA-485-A. The simple topology configuration, the lack of sensitivity to EMC interference and the open protocol have been outstanding features of the combination of RS485 and Modbus RTU protocol for years. If it is necessary to network economical measuring devices with each other, the RS485 interface with Modbus RTU protocol remains the benchmark.