Development Protocol
Function Code Introduction
| Function Code | Description |
|---|---|
| 01 | Read Output Status |
| 02 | Read Input Status |
| 03 | Read Holding Registers |
| 05 | Write Single Output Channel |
| 06 | Write Single Register |
| 0F | Write Multiple Output Channels |
| 10 | Write Multiple Registers |
Register Address Description
| Address (HEX) | Content Stored | Register Value | Access | Modbus Function Code |
|---|---|---|---|---|
| 0x0000 ~ 0x0001 | Output Channel 1 ~ Output Channel 2 Address | 0xFF00: ON; 0x0000: OFF; 0x5500: Toggle | R/W | 0x01, 0x05, 0x0F |
| 0x00FF | Operate All Registers | 0xFF00: All Output ON; 0x0000: All Output OFF; 0x5500: All Output Toggle | W | 0x05, 0x0F |
| 0x0100 ~ 0x0101 | Output Channel 1 ~ Output Channel 2 Address | 0xFF00: Toggle; 0x0000: No Change | W | 0x05 |
| 0x0200 ~ 0x0201 | Output Channel 1 ~ Output Channel 2 Flash ON | Delay time = data × 100 ms Value: 0x0007, delay: 7 × 100 ms = 700 ms | W | 0x05 |
| 0x0400 ~ 0x0401 | Output Channel 1 ~ Output Channel 2 Flash OFF | Delay time = data × 100 ms Value: 0x0007, delay: 7 × 100 ms = 700 ms | W | 0x05 |
| 1x0000 ~ 1x0001 | Input Channel 1 ~ Input Channel 2 Address | Status of input channels 1~2 | R | 0x02 |
| 3x0000 ~ 3x0001 | Analog Input Channel 1 ~ Analog Input Channel 2 Data | Unsigned hexadecimal value | R | 0x04 |
| 4x0000 ~ 4x0001 | Analog Output Channel 1 ~ Analog Output Channel 2 Data | Unsigned hexadecimal value | R/W | 0x03, 0x06, 0x10 |
| 4x1000 ~ 4x1001 | Output Channel 1 ~ Output Channel 2 Control Mode | 0x0000~0x0003 Four control modes | R/W | 0x03, 0x06, 0x10 |
| 4x3000 ~ 4x3001 | Analog Input Channel 1 ~ Analog Input Channel 2 Data Type | 0x0000~0x0004 Five ranges | R/W | 0x03, 0x06, 0x10 |
| 4x2000 | Serial Parameters | High byte: parity (0x00 Low byte: baud rate (0x00 | R/W | 0x03, 0x06 |
| 4x4000 | Device Address | Directly stores Modbus address Device address: 0x0001~0x00FF | R/W | 0x03, 0x06 |
| 4x8000 | Software Version | Convert to decimal and shift decimal point left two places 0x0064 = 100 = V1.00 | R | 0x03 |
Modbus RTU Digital Channel Commands
Control a Single Output Channel
Transmission Code: 01 05 00 00 FF 00 8C 3A
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Write single output channel |
| 00 00 | Address | Register address of output channel to control, 0x0000-0x0001 |
| FF 00 | Command | 0xFF00: ON; 0x0000: OFF; 0x5500: Toggle |
| 8C 3A | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 05 00 00 FF 00 8C 3A
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Write single output channel |
| 00 00 | Address | Register address of output channel to control, 0x0000-0x0001 |
| FF 00 | Command | 0xFF00: ON; 0x0000: OFF; 0x5500: Toggle |
| 8C 3A | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Output channel 0 ON : 01 05 00 00 FF 00 8C 3A
Output channel 0 OFF : 01 05 00 00 00 00 CD CA
Output channel 1 ON : 01 05 00 01 FF 00 DD FA
Output channel 1 OFF : 01 05 00 01 00 00 9C 0A
Control All Relay Output Channels
Transmission Code: 01 05 00 FF FF 00 BC 0A
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Write single output channel |
| 00 FF | Address | Fixed 0x00FF |
| FF 00 | Command | 0xFF00: ON; 0x0000: OFF; 0x5500: Toggle |
| BC 0A | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 05 00 FF FF 00 BC 0A
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Write single output channel |
| 00 FF | Address | Fixed 0x00FF |
| FF 00 | Command | 0xFF00: ON; 0x0000: OFF; 0x5500: Toggle |
| BC 0A | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
All output channels ON : 01 05 00 FF FF 00 BC 0A
All output channels OFF : 01 05 00 FF 00 00 FD FA
All output channels TOGGLE: 01 05 00 FF 55 00 C2 AA
Read Relay Output Channel Status
Transmission Code: 01 01 00 00 00 02 BD CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 01 | Command 01 | Query output channel status |
| 00 00 | Output start address | Register address of output channel, 0x0000-0x0001 |
| 00 08 | Number of output channels | Number of output channels to read, cannot exceed max |
| 3D CC | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 01 01 00 51 88
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 01 | Command 01 | Query output channel status |
| 00 00 | Output start address | Register address of output channel, 0x0000-0x0001 |
| 00 08 | Number of output channels | Number of output channels to read, cannot exceed max |
| 3D CC | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Transmit: 01 01 00 00 00 02 BD CB
Receive: 01 01 01 00 51 88 // All output channel OFF
Transmit: 01 01 00 00 00 02 BD CB
Receive: 01 01 01 01 90 48 // Output channel 0 ON, others OFF
Write Relay Output Channel Status
Transmission Code: 01 0F 00 00 00 02 01 03 9E 96
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 0F | Command 0F | Write output channel status |
| 00 00 | Output start address | Register address of output channel to control, 0x0000-0x0001 |
| 00 08 | Number of output channels | Number of output channels to operate, cannot exceed max |
| 01 | Byte count | Number of status bytes |
| 03 | Output status | Bit0: start output channel; Bit1: next output channel; high bits zero if idle |
| 9E 96 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 0F 00 00 00 02 D4 0A
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 0F | Command 0F | Write multiple relay status command |
| 00 00 | Output address | Register address of output channel, 0x0000-0x0007 |
| 00 02 | Number of outputs | Number of output channels operated |
| D4 0A | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
All output channels ON : 01 0F 00 00 00 02 01 FF 9E D7
All output channels OFF : 01 0F 00 00 00 02 01 00 DE 97
Channel 0 ON; Channel 1 OFF: 01 0F 00 00 00 02 01 01 1F 57
Relay Output Channel Flash ON/OFF Commands
Transmission Code: 01 05 02 00 00 07 8D B0
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Single control command |
| 02 | Sub-command | 02 = Flash ON, 04 = Flash OFF |
| 00 | Output channel address | Output channel address, 0x00~0x07 |
| 00 07 | Interval time | Delay time = data × 100 ms Value: 0x0007, delay: 7 × 100 ms = 700 ms Max flash ON/OFF time 0x7FFF |
| 8D B0 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 05 02 00 00 07 8D B0
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 05 | Command 05 | Single control command |
| 02 | Sub-command | 02 = Flash ON, 04 = Flash OFF |
| 00 | Output channel address | Output channel address, 0x00~0x07 |
| 00 07 | Interval time | Delay time = data × 100 ms Value: 0x0007, delay: 7 × 100 ms = 700 ms Max flash ON/OFF time 0x7FFF |
| 8D B0 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Output channel 0 flash ON: 01 05 02 00 00 07 8D B0 //700MS = 7*100MS = 700MS
Output channel 1 flash ON: 01 05 02 01 00 08 9C 74 //800MS
Output channel 0 flash OFF: 01 05 04 00 00 05 0C F9 //500MS
Output channel 1 flash OFF: 01 05 04 01 00 06 1D 38 //600MS
Read Digital Input Channel Status
Transmission Code: 01 02 00 00 00 02 F9 CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 02 | Command 02 | Read input status command |
| 00 00 | Input start address | Input register address, 0x0000-0x0001 |
| 00 02 | Number of registers | Number of input channels to read, cannot exceed max |
| F9 CB | CRC16 | CRC16 checksum of the first 6 bytes |
Return Code: 01 02 01 00 A1 88
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 02 | Command 02 | Read input status command |
| 01 | Byte count | Total number of bytes in the status information |
| 00 | Query status | Input channel status: Bit0 = start input channel, Bit1= next channel status, etc. high bits zero if idle |
| A1 88 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Transmit: 01 02 00 00 00 02 F9 CB
Return: 01 02 01 00 A1 88 //Inputs are all untriggered
Transmit: 01 02 00 00 00 02 F9 CB
Return: 01 02 01 01 60 48 //Channel 1 input is triggered, and the rest of channels are not triggered
Read Relay Output Channel Control Mode
Transmit: 01 03 10 00 00 02 C0 CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00 indicates broadcast address; 0x01-0xFF indicate device address |
| 03 | 03 Command | Read Holding Registers |
| 10 00 | Register start address | 0x1000-0x1007 corresponds to output channels 1~8 |
| 00 02 | Number of registers | Number of registers to read, maximum 8 channels |
| C0 CB | CRC16 | CRC16 checksum of the first 6 bytes |
Return code: 01 03 04 00 00 00 00 FA 33
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | Command 03 | Read holding registers |
| 04 | Byte count | Total number of bytes in the status information |
| 00 00 ...... 00 00 | Control mode | Control mode for output channels 1 0x0000: Normal mode – output controlled directly by command; 0x0001: Linkage mode – output follows corresponding input; 0x0002: Toggle mode – output toggles on each input pulse; 0x0003: Edge Trigger Mode – output toggles on each input level change |
| FA 33 | CRC16 | CRC16 checksum of the first 6 bytes |
Note
Except for Link mode, all other modes also support command control of output channels.
Example: Device with address 1
Read output channel 1 control mode : 01 03 10 00 00 01 80 CA
Read output channel 2 control mode : 01 03 10 01 00 01 D1 0A
Set Single Output Channel Control Mode
Transmission Code: 01 06 10 00 00 01 4C CA
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 10 00 | Register start address | 0x1000-0x1007 corresponds to output channels 1~8 control mode |
| 00 01 | Control mode | Control modes for output channels 1 0x0000: Normal mode – output controlled directly by command; 0x0001: Linkage mode – output follows corresponding input; 0x0002: Toggle mode – output toggles on each input pulse; 0x0003: Edge Trigger Mode – output toggles on each input level change |
| 4C CA | CRC16 | CRC16 checksum of the first 6 bytes of data |
Note
Except for Linkage mode, all other modes also support command control of output channels.
Return Code: 01 06 10 00 00 01 4C CA
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 10 00 | Register start address | 0x1000-0x1001 corresponds to output channels 1~2 control mode |
| 00 01 | Control mode | Output channel control modes, 0x0000~0x0003 indicate four control modes |
| 4C CA | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set output channel 1 to Linkage mode: 01 06 10 00 00 01 4C CA
Set output channel 2 to Toggle mode: 01 06 10 01 00 02 5D 0B
Set Multiple Output Channel Control Modes
Transmit: 01 10 10 00 00 02 04 00 01 00 01 AE 6F
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 10 00 | Register start address | 0x1000-0x1001 corresponds to output channels 1~2 control mode |
| 00 02 | Number of registers | Number of registers to set, up to 2 channels |
| 04 | Byte Count | Number of output bytes |
| 00 01 ...... 00 01 | Control mode | Control mode for output channels 1 0x0000: Normal mode – output controlled directly by command; 0x0001: Linkage mode – output follows corresponding input; 0x0002: Toggle mode – output toggles on each input pulse; 0x0003: Edge Trigger Mode – output toggles on each input level change |
| AE 6F | CRC16 | CRC16 checksum of the first 6 bytes |
Note
Except for Linkage mode, all other modes also support command control of output channels.
Return Code: 01 10 10 00 00 02 45 08
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 10 00 | Register start address | 0x1000-0x1007 corresponds to output channels 1~8 control mode |
| 00 02 | Number of registers | Number of registers to set, up to 8 channels |
| 45 08 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set channels 1-2 output as Linkage mode: 01 10 10 00 00 02 04 00 01 00 01 AE 6F
Set channels 1-2 output as Normal mode: 01 10 10 00 00 02 04 00 00 00 00 3E 6F
Modbus RTU Analog Channel Commands
Set Single Analog Output Channel
Send code: 01 06 00 00 03 E8 89 74
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 00 00 | Register address | 0x0000-0x0007 corresponds to output channels 1~8 |
| 03 E8 | Set Value | Hex value, unit μA, high byte first 0x03E8 = 1000 μA = 1 mA |
| 89 74 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 06 00 00 03 E8 89 74
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 00 00 | Register address | 0x0000-0x0007 corresponds to output channels 1~8 |
| 03 E8 | Set Value | Hex value, unit μA, high byte first 0x03E8 = 1000 μA = 1 mA |
| 89 74 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set channel 1 output 1mA : 01 06 00 00 03 E8 89 74
Set channel 2 output 5mA : 01 06 00 01 13 88 D5 5C
Set Multiple Analog Output Channels
Transmit: 01 10 00 00 00 02 04 03 E8 03 E8 73 61
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 00 00 | Register Start Address | 0x0000 - 0x0002 correspond to output channels 1~2 |
| 00 02 | Number of Registers | Number of registers set, cannot exceed maximum channel count |
| 04 | Byte Count | Number of output bytes |
| 03 E8 ...... 03 E8 | Values | Start channel analog output …… Final channel analog output Hex, μA, high byte first, 0x03E8 = 1000 μA = 1 mA |
| 73 61 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 10 00 00 00 02 41 C8
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 00 00 | Register start address | 0x0000-0x0007 corresponds to output channels 1~8 |
| 00 02 | Number of Registers | Number of registers set, cannot exceed maximum channel count |
| 41 C8 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set channels 1-2 output 1mA : 01 10 00 00 00 02 04 03 E8 03 E8 73 61
Set channels 1-2 output 2mA : 01 10 00 00 00 02 04 07 D0 07 D0 F0 8E
Read Analog Output
Transmit: 01 03 00 00 00 02 C4 0B
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | Command 03 | Read holding registers |
| 00 00 | Starting register address | 0x0000 - 0x0001 correspond to relay control mode for channels 1~2 |
| 00 02 | Number of registers | Number of registers to read, cannot exceed maximum channel count |
| C4 0B | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 03 04 03 E8 03 E8 7A FD
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | Command 03 | Read holding registers |
| 04 | Byte count | Total number of bytes in the status information |
| 03 E8 ...... 03 E8 | Output values | Start channel analog output …… Final channel analog output Hex, μA, high byte first, 0x03E8 = 1000 μA = 1 mA |
| 7A FD | CRC16 | CRC16 checksum of the first 6 bytes |
Example: Device with address 1
Read channel 1 data type : 01 03 00 00 00 01 84 0A
Read channel 2 data type : 01 03 00 01 00 01 D5 CA
Read Analog Input
Transmission Code: 01 04 00 00 00 02 71 CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 04 | 04 Command | Read Input Registers |
| 00 00 | Starting register address | 0x0000 - 0x0001 correspond to relay control mode for channels 1~2 |
| 00 02 | Number of registers | Number of registers to read, cannot exceed maximum channel count |
| 71 CB | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 01 04 04 00 00 00 00 FB 84
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 04 | 04 Command | Read Input Registers |
| 04 | Byte Count | Data length |
| 00 00 ...... 00 00 | Register data | Indicates the analog values from channels 0 - 2 Unsigned 16-bit per channel, high byte first Data range depends on the data type |
| FB 84 | CRC16 | CRC16 checksum of the first 6 bytes |
Example: Device with address 1
Read analog input channel 1: 01 04 00 00 00 01 31 CA
Read analog input channel 2: 01 04 00 01 00 01 60 0A
Read Analog Input Channel Data Type
Transmit: 01 03 30 00 00 02 CB 0B
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | Command 03 | Read holding registers |
| 30 00 | Register start address | 0x3000-0x3001 corresponds to input channels 1~2 |
| 00 02 | Number of registers | Number of registers to read, cannot exceed maximum channel count |
| CB 0B | CRC16 | CRC16 checksum of the first 6 bytes |
Return: 01 03 04 00 02 00 02 DA 32
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | Command 03 | Read holding registers |
| 04 | Byte count | Total number of bytes in the status information |
| 00 02 ...... 00 02 | Data type | Data type for channels 0 0x0000: **Range 0 0x0001: **Range 1 0x0002: **Range 0 0x0003: **Range 4 0x0004: Raw code output 0~4096, requires linear conversion |
| DA 32 | CRC16 | CRC16 checksum of the first 6 bytes |
Example: Device with address 1
Read analog input channel 1 data type : 01 03 10 00 00 01 80 CA
Read analog input channel 2 data type : 01 03 10 01 00 01 D1 0A
Set Single Analog Input Channel Data Type
Transmit: 01 06 30 00 00 03 C6 CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 30 00 | Register start address | 0x3000-0x3001 corresponds to input channels 1~2 data type |
| 00 03 | Channel data type | Data type for channels, 0x0000 ~ 0x0004 represents five ranges: 0x0000: **Range 0 0x0001: **Range 1 0x0002: **Range 0 0x0003: **Range 4 0x0004: Raw code output 0~4096, requires linear conversion |
| C6 CB | CRC16 | CRC16 checksum of the first 6 bytes |
Return Code: 01 06 30 00 00 03 C6 CB
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Write single register command |
| 30 00 | Register start address | 0x3000-0x3001 corresponds to input channels 1~2 data type |
| 00 03 | Channel data type | Data type for channels, 0x0000 ~ 0x0004 represents five ranges: 0x0000: **Range 0 0x0001: **Range 1 0x0002: **Range 0 0x0003: **Range 4 0x0004: Raw code output 0~4096, requires linear conversion |
| C6 CB | CRC16 | CRC16 checksum of the first 6 bytes |
Example: Device with address 1
Set channel 1 data type to 0~20mA : 01 06 30 00 00 02 07 0B
Set channel 2 data type to 4~20mA : 01 06 30 00 00 03 C6 CB
Set Multiple Analog Input Channel Data Type
Transmit: 01 10 30 00 00 02 04 00 03 00 03 17 AF
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 30 00 | Register start address | 0x3000-0x3001 corresponds to input channels 1~2 data type |
| 00 02 | Number of Registers | Number of registers set, cannot exceed maximum channel count |
| 04 | Byte Count | Number of output bytes |
| 00 03 ...... 00 03 | Data type | Data types for channels 0 0x0000: **Range 0 0x0001: **Range 1 0x0002: **Range 0 0x0003: **Range 4 0x0004: Raw code output 0 |
| 17 AF | CRC16 | CRC16 checksum of the first 6 bytes |
Return Code: 01 10 30 00 00 02 4E C8
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 10 | Write Multiple Registers Command | |
| 30 00 | Register start address | 0x3000-0x3001 corresponds to input channels 1~2 data type |
| 00 02 | Number of Registers | Number of registers set, cannot exceed maximum channel count |
| 4E C8 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set channels 1-2 data type to 4~20mA : 01 10 30 00 00 02 04 00 03 00 03 17 AF
Set channels 1-2 data type to 1~5V : 01 10 30 00 00 02 04 00 01 00 01 37 AE
Modbus RTU Communication Commands
Set Baud Rate Command
Transmission Code: 00 06 20 00 00 05 43 D8
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Set baud rate, device address |
| 20 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 | Parity Mode | 0x00 for no parity, 0x01 for odd parity, 0x02 for even parity |
| 05 | Baud rate value | Corresponding baud rates: 0x00:4800, 0x01:9600, 0x02:19200, 0x03:38400, 0x04:57600, 0x05:115200, 0x06:128000, 0x07:256000 |
| 43 D8 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 00 06 20 00 00 05 43 D8
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Set baud rate, device address |
| 20 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 | Parity Mode | 0x00 for no parity, 0x01 for odd parity, 0x02 for even parity |
| 05 | Baud rate value | Corresponding baud rates: 0x00:4800, 0x01:9600, 0x02:19200, 0x03:38400, 0x04:57600, 0x05:115200, 0x06:128000, 0x07:256000 |
| 43 D8 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Set baud rate 4800 : 00 06 20 00 00 00 83 DB
Set baud rate 9600 : 00 06 20 00 00 01 42 1B
Set baud rate 19200 : 00 06 20 00 00 02 02 1A
Set baud rate 38400 : 00 06 20 00 00 03 C3 DA
Set the baud rate as 57600: 00 06 20 00 00 04 82 18
Set the baud rate as 115200: 00 06 20 00 00 05 43 D8
Set the baud rate as 128000: 00 06 20 00 00 06 03 D9
Set the baud rate as 256000: 00 06 20 00 00 07 C2 19
Set Device Address Command
Transmission Code: 00 06 40 00 00 01 5C 1B
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Set baud rate, device address |
| 40 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 01 | Device address | Device address set, 0x0001-0x00FF |
| 5C 1B | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 00 06 40 00 00 01 5C 1B
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 06 | Command 06 | Set baud rate, device address |
| 40 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 01 | Device address | Device address set, 0x0001-0x00FF |
| 5C 1B | CRC16 | CRC16 checksum of the first 6 bytes |
Example: Device with address 1
Set the device address to 0x01: 00 06 40 00 00 01 5C 1B
Set the device address to 0x02: 00 06 40 00 00 02 1C 1A
Set the device address to 0x03: 00 06 40 00 00 03 DD DA
Read Device Address Command
Transmission code: 00 03 40 00 00 01 90 1B
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | 03 Command | Read device address command |
| 40 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 01 | Byte Count | Fixed 0x0001 |
| 90 1B | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return code: 01 03 02 00 01 79 84
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | 03 Command | Read software version, read device address command |
| 02 | Byte count | Returned byte count |
| 00 01 | Device address | Device address set, 0x0001-0x00FF |
| 79 84 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 2
Transmission Code: 00 03 40 00 00 01 90 1B
Receive: 00 03 02 00 02 04 45 //Address: 0x02
Read Software Version Command
Transmission Code: 00 03 80 00 00 01 AC 1B
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | 03 Command | Read software version, read device address command |
| 80 00 | Command register | 0x2000: set baud rate; 0x4000: set device address; 0x8000: read software version |
| 00 01 | Byte Count | Fixed 0x0001 |
| AC 1B | CRC16 | CRC16 checksum of the first 6 bytes of data |
Return Code: 00 03 02 00 C8 84 12
| Field | Description | Notes |
|---|---|---|
| 00 | Device Address | 0x00: broadcast; 0x01-0xFF: device address |
| 03 | 03 Command | Read software version, read device address command |
| 02 | Byte Count | Returned byte count |
| 00 C8 | Software version | Convert to decimal and shift decimal point left two places: 0x00C8 = 200 = V2.00 |
| 84 12 | CRC16 | CRC16 checksum of the first 6 bytes of data |
Example: Device with address 1
Transmission Code: 00 03 80 00 00 01 AC 1B
Return Code: 00 03 02 00 64 84 6F //0x0064 = 100 =V1.00
Exception Function Code Introduction
If the received command is incorrect or an exception occurs, the device will return an exception response. The exception response format is as follows:
Return Code: 01 85 03 02 91
| Field | Description | Notes |
|---|---|---|
| 01 | Device Address | 0x00 indicates broadcast address; 0x01-0xFF indicate device address |
| 85 | Exception Function Code | Exception function code = Request function code + 0x80 |
| 03 | Byte Count | Exception code |
| 02 91 | CRC16 | CRC16 checksum of the first 6 bytes of data |
The exception code is a single-byte value indicating the type of error. Several common exception codes defined by the Modbus protocol:
| Exception Code | Name | Description |
|---|---|---|
| 0x01 | Illegal Function | The requested function code is not supported |
| 0x02 | Illegal Data Address | The requested data address is incorrect |
| 0x03 | Illegal Data Value | The requested data value or operation cannot be performed |
| 0x04 | Server Failure | Server device failure |
| 0x05 | Acknowledge | Request received and processing |
| 0x06 | Device Busy | Device is busy and cannot execute the requested operation |