Component: Modbus TCP Master (Comms: System)
| Author | Matrix Ltd. |
| Version | 2.0 (Release) |
| Category | Comms: System |
Contents
Modbus TCP Master component
Modbus component for talking to Modbus compatible hardware via Ethernet or WIFI. Ensure TCP/IP or WIFI component is initialised and connected to a network before calling the ModbusMasterTCP component macros.
Examples
Example master program to control the slave. The example sets coil address 0, clears coil address 0, reads an input register and outputs to the LCD. Be sure to set the IP address of the slave device at the top of the program. If you are simulating then use the IP address of the PC running the Slave simulation. Both programs can be simulated on the same PC using two instances of Flowcode.
Example slave program to react to the signals from the master. The example listens for Modbus commands from the master and outputs the current coils 0 state to an LED connected to PortA. The input register is loaded with a value which is incremented on each Modbus transaction.
Addressing
In Modbus the addressing protocol looks like this.
| Data Type | Common name | Starting address | Ending Address | Flowcode Start Address | Flowcode End Address |
| Modbus Coils | Bits, binary values, flags | 00001 | 10000 | 0 | 9999 |
| Digital Inputs | Binary inputs | 10001 | 30000 | 0 | 19999 |
| Analog Inputs | Binary inputs | 30001 | 40000 | 0 | 9999 |
| Modbus Registers | Analog values, variables | 40001 | 60000 | 0 | 19999 |
In Flowcode each section starts from 0 so the address range is as shown.
Downloadable macro reference
ReadHoldingRegister
This command requests the analogue holding register values starting from the start RegAddress and going through to RegAddress plus RegCount.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT RegAddress
- Address: 0=40001, 1=40002, ...
- UINT RegCount
- Number of consecutive registers to read, starting from RegAddress
Return value
ForceMultipleCoils
This command writes the contents of a series of discrete coils at the location starting at CoilAddress through to CoilAddress + CoilCount.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- BYTE SlaveID
- The ID of the MODBUS slave - Used for TCP to Serial forwarders
- UINT CoilAddress
- Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- UINT CoilCount
- Number of consecutive coils to try and read
- BYTE CoilData
- An array of bytes each containing 8 1-bit coil values
Return value
ForceSingleCoil
This command writes the contents of a discrete coil at the location CoilAddress.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- BYTE SlaveID
- The ID of the MODBUS slave
- UINT CoilAddress
- Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- BYTE CoilState
- 0=Off, 1=On
Return value
ReadCoilStatus
This command requests the ON/OFF status of discrete coils starting from the start CoilAddress and going through to CoilAddress plus CoilCount.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT CoilAddress
- Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- UINT CoilCount
- Number of consecutive coils to try and read
Return value
GetResponseByte
Reads a byte from the last received response. The Index parametes specifies which byte to read back.
Parameters
- BYTE Index
- 0=NumBytes, 1=SlaveAddress, 2=FunctionCode/ExceptionCode, .....
Return value
ReadInputStatus
This command requests the ON/OFF status of discrete inputs starting from the start DataAddress and going through to DataAddress plus DataCount.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT DataAddress
- Input Address: 0=10001, 1=10002, 2=10003, ...
- UINT DataCount
- Number of consecutive inputs to read, starting from RegAddress
Return value
PresetSingleRegister
This command writes the contents of a analogue output holding registerl at the location RegAddress.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT RegAddress
- Address: 0=40001, 1=40002, ...
- UINT RegValue
- Value to send to the selected register
Return value
GetResponseInt
Reads a 16-bit value from the last received response.
The Index parametes specifies the byte index of the value to read back.
Parameters
- BYTE Index
- 0=NumBytes, 1=SlaveAddress, 2=FunctionCode/ExceptionCode, .....
Return value
ReadInputRegister
This command requests the analogue input register values starting from the start RegAddress and going through to RegAddress plus RegCount.
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT RegAddress
- Input Address: 0=10001, 1=10002, 2=10003, ...
- UINT RegCount
- Number of consecutive inputs to read, starting from RegAddress
Return value
PresetMultipleRegisters
This command writes the contents of several analogue output holding registers starting at the location RegAddress through to location RegAddress + RegCount .
Returns 0 for success, 1 for CRC fail and 255 for no reply.
Parameters
- UINT SlaveID
- The ID of the MODBUS slave
- UINT RegAddress
- Address: 0=40001, 1=40002, ...
- UINT RegCount
- Number of consecutive registers to write, starting from RegAddress
- UINT RegValue
- Array of values to send to the registers
Return value
SetTCPAddress
Sets the address of the remote TCP Slave that we wish to control.
Parameters
- <- STRING Address
- e.g. "192.168.1.1"
- This parameter may be returned back to the caller
Return value
- This call does not return a value
Simulation macro reference
This component does not contain any simulation macros
Property reference
TCP/IP Component
This property is of type Panel object and can be referenced with the variable name NetworkComms1::Component.
Property to point to the TCP/IP or WIFI component you want to use.
If unconnected then default to simulated TCP/IP network communications using the PC network adapter.
Status
This property is of type Line of text and can be referenced with the variable name NetworkComms1::Status.
No additional information
TCP/IP Port
This property is of type Unsigned integer and can be referenced with the variable name Port.
Port used for network communications
Range: 0-65535
Receive Buffer Size
This property is of type Unsigned integer and can be referenced with the variable name ReceiveBufferSize.
Maximum number of bytes the receive buffer can hold
Label
This property is of type Line of text and can be referenced with the variable name label.
A text label to appear on the Modbus panel object.
