Lumel N31U - Description of the MODBUS Protocol Implementation

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N31U User manual
5.5.2 Description of the MODBUS protocol implementation.
The implemented protocol is compliant with the PI-MBUS-300 Rev G speci-
cation of Modicon.
It is important to keep in mind when conguring the parameters that the devi-
ces using the same bus must meet the following requirements:
• Have a unique address, di󰀨erent from the addresses of other devices con-
nected to the network.
• The same baud rate.
• The same type of transmission mode (single data frame format).
The N31U meters enable programming the following parameters of the RS-
485 link:
• Meter address: 1...247.
• Baud rate: 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600,
115200 [b/s].
• Operation mode: RTU frame format 8n1, 8n2, 8o1, 8e1.
• Maximum response time: 50 ms.
Fig. 13: Connecting the RS-485 interface.