Component: Modbus TCP Slave (Comms: System)

Author	Matrix Ltd.
Version	2.1
Category	Comms: System

Modbus TCP Slave component

Modbus component for creating Modbus compatible slave hardware via Ethernet or WIFI. Ensure TCP/IP or WIFI component is initialised and connected to a network before calling the ModbusSlaveTCP component macros.

Component Source Code

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

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

CheckForIncoming

	CheckForIncoming
Checks for an incoming message and if the data address is within range then also automatically replies with the correct reply. Returns 0 if no comms received, 1 for a succesful transaction, 255 for an error.
- BYTE	Return

GetLastIncoming

	GetLastIncoming
Gets a value from the last incoming command. Index 0 = 0 Read / 1 Write Index 1 = 0 Coils / 1 DigInput / 2 AnInput / 3 Register Index 2 = Address Index 3 = Number
- BYTE	Index
Range: 0-3
- UINT	Return

Initialise

	Initialise
Starts up the UART to allow communications and initialises the states of the various Modbus Coils, Inputs and Registers to 0.
- VOID	Return

ReadAnalogInput

	ReadAnalogInput
Reads the value of a single analogue input.
- UINT	Address
Coil Address
- UINT	Return

ReadCoils

	ReadCoils
Reads the state of a single digital coil. Can pack a max of 8-bits together in a single operation
- UINT	StartAddress
Coil Address Range 0 to (NumCoils - 1)
- BYTE	AddressCount
Range 1-8
- BYTE	Return

ReadDigitalInputs

	ReadDigitalInputs
Reads the state of a single digital input. Can pack a max of 8-bits together in a single operation
- UINT	StartAddress
Coil Address Range 0 to (NumCoils - 1)
- BYTE	AddressCount
Range 1-8
- BYTE	Return

ReadHoldingRegister

	ReadHoldingRegister
Reads the value of a single holding register.
- UINT	Address
Coil Address
- UINT	Return

SetAnalogInput

	SetAnalogInput
Sets the state of a single analogue input.
- UINT	Address
Coil Address
- UINT	Value
Analogue Value range 0 - 65535
- VOID	Return

SetCoil

	SetCoil
Sets the state of a single digital coil.
- UINT	Address
Coil Address
- BYTE	State
0=off, 1=on
- VOID	Return

SetDigitalInput

	SetDigitalInput
Sets the state of a single digital input.
- UINT	Address
Coil Address
- BYTE	State
0=off, 1=on
- VOID	Return

SetHoldingRegister

	SetHoldingRegister
Sets the state of a single holding register.
- UINT	Address
Coil Address
- UINT	Value
Analogue Value range 0 - 65535
- VOID	Return

SetSlaveAddress

	SetSlaveAddress
Allows the slave address to be overridden from the default slave address specified in the component property. The number of bytes used for the address is fixed by the Slave ID Bytes property to save on RAM usage.
- UINT	SlaveAddress
- 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 reply, in mS
	Slave Address
Address of the slave. Range: 0-255
	Maintain Stats
Controls if the last command from the master is logged allowing for easier value updates. No - Do not log commands Yes - Commands are logged and available via the GetLastIncoming macro
	Open and Close Socket
	Simulation Properties
	Label
A text label to appear on the Modbus panel object.
	Modbus Coils - Single bit values
	Starting Address
Start address of the Modbus coils. Referenced from 0. For example Slave 1 might have 100 coils addressed 0-99 Start Address = 0 Slave 2 might have 100 coils addressed 100-199 Start Address = 100
	Number of Addresses
Specifies how many Coils are available on the slave. Each address consumes a single bit of RAM, 8 Addresses are packed together into a single RAM Byte.
	Digital Inputs - Single bit values
	Starting Address
Start address of the Modbus digital inputs. Referenced from 0. For example Slave 1 might have 100 inputs addressed 0-99 Start Address = 0 Slave 2 might have 100 inputs addressed 100-199 Start Address = 100
	Number of Addresses
Specifies how many Digital Inputs are available on the slave. Each address consumes a single bit of RAM, 8 Addresses are packed together into a single RAM Byte.
	Analog Inputs - 16-bit values
	Starting Address
Start address of the Modbus analogue inputs. Referenced from 0. For example Slave 1 might have 100 inputs addressed 0-99 Start Address = 0 Slave 2 might have 100 inputs addressed 100-199 Start Address = 100
	Number of Addresses
Specifies how many 16-bit analogue inputs are available on the slave. Each address consumes two RAM Bytes.
	Holding Registers - 16-bit values
	Starting Address
Start address of the Modbus registers. Referenced from 0. For example Slave 1 might have 100 registers addressed 0-99 Start Address = 0 Slave 2 might have 100 registers addressed 100-199 Start Address = 100
	Number of Addresses
Specifies how many 16-bit holding registers are available on the slave. Each address consumes two RAM Bytes.