Component: Modbus TCP Master (Comms: System)

Author	Matrix Ltd.
Version	2.1
Category	Comms: System

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.

Component Source Code

Please click here to download the component source project: FC_Comp_Source_ModbusTCP.fcfx

Please click here to view the component source code (Beta): FC_Comp_Source_ModbusTCP.fcfx

Detailed description

No detailed description exists yet for this component

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.

Modbus TCP Master Example

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.

Modbus TCP Slave Example

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.

Macro reference

GetResponseByte

	GetResponseByte
Reads a byte from the last received response. The Index parametes specifies which byte to read back.
- BYTE	Index
0=SlaveAddress, 1=FunctionCode/ExceptionCode, 2=DataBytes, 3=data0, 4=data1, ..
- BYTE	Return

GetResponseInt

	GetResponseInt
Reads a 16-bit value from the last received response. The Index parametes specifies the byte index of the value to read back.
- BYTE	Index
3=data0, 5=data1, 7=data2, ..
- UINT	Return

ReadAnalogInput

	ReadAnalogInput
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.
- 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
- BYTE	Return

ReadCoils

	ReadCoils
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.
- 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
- BYTE	Return

ReadDigitalInputs

	ReadDigitalInputs
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.
- 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
- BYTE	Return

ReadHoldingRegister

	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.
- 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
- BYTE	Return

SetCoil

	SetCoil
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.
- BYTE	SlaveID
The ID of the MODBUS slave
- UINT	CoilAddress
Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- BYTE	CoilState
0=Off, 1=On
- BYTE	Return

SetCoils

	SetCoils
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.
- 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
- BYTE	Return

SetHoldingRegister

	SetHoldingRegister
This command writes the contents of a analogue output holding register at the location RegAddress. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	RegAddress
Address: 0=40001, 1=40002, ...
- UINT	RegValue
Value to send to the selected register
- BYTE	Return

SetHoldingRegisters

	SetHoldingRegisters
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.
- 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
- BYTE	Return

SetTCPAddress

	SetTCPAddress
Sets the address of the remote TCP Slave that we wish to control.
- STRING	Address
e.g. "192.168.1.1"
- VOID	Return

Property reference

	Properties
	Modbus TCP/IP Properties
	LinkTo
	Status
Shows the state of the network comms component to verify everything is configured correctly.
	TCP/IP Port
Port used for network communications Range: 0-65535
	Receive Buffer Size
Maximum number of bytes the receive buffer can hold
	Receive Timeout
Maximum time to wait for network reply, in mS
	Simulation Properties
	Label
A text label to appear on the Modbus panel object.