Modbus¶
MODBUS communication protocol¶
| Important: Please read out the MODBUS byte order of the RMS device with RMS-CONFIG prior to any programming. |
|---|
For direct connection to other systems, the device provides a MODBUS TCP server. Following data is available via MODBUS communication:
| Protocol | MODBUS TCP |
|---|---|
| TCP Port | 502 |
When reading out data from the input register select the index=-1.¶
MODBUS register
Device data (FC4: Read Input Registers)
| 10000 | 16 | Digital inputs | Unsigned 16 Bit | Bit 0 = Input 1 / Bit 1 = Input 2 |
|---|---|---|---|---|
Measurement values (FC2: Read Discrete Inputs)
| 30000 | 2 | Serial number | Unsigned 32 Bit | SN in Hex: e.g. 01ACCBE1 = 28101601 |
|---|---|---|---|---|
The RMS LAN devices (except the RMS-Converter) are based on a Little Endian memory organisation (The device firmware provides the MODBUS information starting with the most significant byte.)
| 31001 | 0 | 0x0000 | 31001 | 13378 | 0x3442 |
|---|---|---|---|---|---|
| 31002 | 13378 | 0x3442 | 31002 | 0 | 0x0000 |
| 31003 | 0 | 0x0000 | 31003 | 31300 | 0x7A44 |
| 31004 | 31300 | 0x7A44 | 31004 | 0 | 0x0000 |
| Byte Swap (Mixed Endian) | Byte and Word Swap (Big Endian) | ||||
| 31001 | 0 | 0x0000 | 31001 | 16948 | 0x4234 |
| 31002 | 16948 | 0x4234 | 31002 | 0 | 0x0000 |
| 31003 | 0 | 0x0000 | 31003 | 17530 | 0x447A |
| 31004 | 17530 | 0x447A | 31004 | 0 | 0x0000 |
Connection timeout: When TCP connection is open and for more than 30 seconds no communication is performed, the device automatically closes the TCP connection. In case of a communication interruption, this prevents the socket being blocked.
Additional MODBUS details can be found here: MODBUS in RMS.
Updated: 13.12.2023.