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.
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.
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
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Return |
GetLastIncoming
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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
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Index |
| Range: 0-3 | |
 - UINT
|
Return |
Initialise
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Initialise |
| Starts up the UART to allow communications and initialises the states of the various Modbus Coils, Inputs and Registers to 0. | |
 - VOID
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Return |
ReadAnalogInput
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ReadAnalogInput |
| Reads the value of a single analogue input. | |
| - UINT
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Address |
| Coil Address | |
| - UINT
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Return |
ReadCoils
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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
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AddressCount |
| Range 1-8 | |
| - BYTE
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Return |
ReadDigitalInputs
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ReadDigitalInputs |
| Reads the state of a single digital input. Can pack a max of 8-bits together in a single operation | |
| - UINT
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StartAddress |
| Coil Address Range 0 to (NumCoils - 1) | |
| - BYTE
|
AddressCount |
| Range 1-8 | |
| - BYTE
|
Return |
ReadHoldingRegister
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ReadHoldingRegister |
| Reads the value of a single holding register. | |
| - UINT
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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
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|
SetCoil |
| Sets the state of a single digital coil. | |
| - UINT
|
Address |
| Coil Address | |
| - BYTE
|
State |
| 0=off, 1=on | |
| - VOID
|
Return |
SetDigitalInput
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SetDigitalInput |
| Sets the state of a single digital input. | |
| - UINT
|
Address |
| Coil Address | |
| - BYTE
|
State |
| 0=off, 1=on | |
| - VOID
|
Return |
SetHoldingRegister
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SetHoldingRegister |
| Sets the state of a single holding register. | |
| - UINT
|
Address |
| Coil Address | |
| - UINT
|
Value |
| Analogue Value range 0 - 65535 | |
| - VOID
|
Return |
SetSlaveAddress
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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
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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 | |
|
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Receive Buffer Size |
| Maximum number of bytes the receive buffer can hold | |
|
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Receive Timeout |
| Maximum time to wait for reply, in mS | |
|
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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 | |
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Open and Close Socket |
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Simulation Properties |
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Label |
| A text label to appear on the Modbus panel object. | |
|
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Modbus Coils - Single bit values |
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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 | |
|
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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. | |
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Digital Inputs - Single bit values |
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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 | |
|
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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. | |
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Analog Inputs - 16-bit values |
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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 | |
|
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Number of Addresses |
| Specifies how many 16-bit analogue inputs are available on the slave. Each address consumes two RAM Bytes. | |
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Holding Registers - 16-bit values |
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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 | |
|
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Number of Addresses |
| Specifies how many 16-bit holding registers are available on the slave. Each address consumes two RAM Bytes. | |