Hello everyone, I have a question about the requirements for the RS-485 mode in this module. According to the manual, when RS-485 mode is selected (with the appropriate jumper settings), the module requires a 2-wire connection to be wired to RJ-45 Pin 1 (Data+ or TXDRXD+) and Pin 8 (Data- or TXDRXD-), with the option to include a GND wire to Pin 5 (separate from the screen wire). If a device is using 4 wires for the interface, the MCM module is not compatible with RS-485 and the options are to switch to RS-422, configure the device to half duplex mode, or use a gateway to provide only the necessary + and - wires to the MCM side. Can the MVI56E-MCM module support RS-485 full duplex without any additional conversion in between? Thank you.
Upon skimming the manual, it verifies your understanding that the module does not support full duplex RS-485 because it is tailored for the Modbus protocol. Modbus follows a poll/response approach where the master device waits for the slave's response before moving on to the next device. Due to this, separate Transmit and receive buses are not necessary as the master device will only transmit after receiving a response or when a timeout occurs. The Modbus protocol does not cater to full-duplex operations. In the case of the MVI56E-MCM module, it does not operate in full duplex mode but can be converted to half duplex 2-wire via jumpering. It is not possible to implement full duplex without conversion. If you are looking for a full duplex protocol other than Modbus for RS-485 implementation, is there a specific one you have in mind?
Thank you for your prompt reply, danw. Our primary focus lies on utilizing Modbus for our project. To clarify, when I mentioned "full duplex," I actually meant devices with 4-wire connections for RS-485 communication. It appears that certain devices may feature 4 terminals for the RS-485 Modbus interface, requiring a "Gateway" as indicated in the MCM user manual. You can refer to this resource for more information: [link]. Just to confirm, for the MCM module with RS-485 configuration, only pin 1 & 8 (with 5 as an option) on the RJ45 port are necessary; please avoid shorting pin 1 with 2 and pin 8 with 6. We are preparing for testing and aim to finalize the design soon.
Hi there, you've outlined the requirements quite accurately. Unfortunately, the MVI56E-MCM module only supports RS-485 in half-duplex mode natively. Due to its internal design, it cannot facilitate full duplex without external help. Therefore, your options would indeed be to either switch to RS-422, reconfigure your device to half duplex, or use a gateway to convert the signals. The purpose here is to ensure data integrity for your application which is why these stringent requirements exist. Hope this clarifies your query!
Hi there, the MVI56E-MCM module in its original configuration specifically supports RS-485 in a 2-wire, half-duplex setup, as you've stated. The physically wired 4-wire full-duplex RS-485 communications typically require two separate pairs of signals, 'TX+/TX-' and 'RX+/RX-' which this module may not inherently support. To stay in RS-485, you might need to consider an external converter that can convert the 4-wire duplex RS-485 to a 2-wire duplex RS-485 setup, viewable by the MCM module. However, it's always advisable to connect with the module's manufacturer or your automation vendor to confirm potential compatibility issues before proceeding.
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Answer: - No, the MVI56E-MCM module does not support RS-485 full duplex mode directly. If a device is using 4 wires for the interface, options include switching to RS-422, configuring the device to half duplex mode, or using a gateway to provide only the necessary + and - wires to the MCM module.
Answer: - The module requires a 2-wire connection to be wired to RJ-45 Pin 1 (Data+ or TXDRXD+) and Pin 8 (Data- or TXDRXD-), with the option to include a GND wire to Pin 5 (separate from the screen wire) when RS-485 mode is selected.
Answer: - If a device is using 4 wires for the interface, the MCM module is not compatible with RS-485. Options include switching to RS-422, configuring the device to half duplex mode, or using a gateway to provide only the necessary + and - wires to the MCM side.
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