Component: Modbus TCP Slave (Comms: System)
| Author | Matrix Ltd. |
| Version | 2.0 (Release) |
| Category | Comms: System |
Contents
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.
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
Reads the value of a single holding register.
Parameters
- UINT Address
- Coil Address
Return value
ReadCoilStates
Reads the state of a single digital coil.
Can pack a max of 8-bits together in a single operation
Parameters
- UINT StartAddress
- Coil Address Range 0 to (NumCoils - 1)
- BYTE AddressCount
- Range 1-8
Return value
ReadAnalogueInput
Reads the value of a single analogue input.
Parameters
- UINT Address
- Coil Address
Return value
ReadInputStates
Reads the state of a single digital input.
Can pack a max of 8-bits together in a single operation
Parameters
- UINT StartAddress
- Coil Address Range 0 to (NumCoils - 1)
- BYTE AddressCount
- Range 1-8
Return value
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.
Parameters
- UINT SlaveAddress
Return value
- This call does not return a value
SetCoilState
Sets the state of a single digital coil.
Parameters
- UINT Address
- Coil Address
- BYTE State
- 0=off, 1=on
Return value
- This call does not return a value
SetInputState
Sets the state of a single digital input.
Parameters
- UINT Address
- Coil Address
- BYTE State
- 0=off, 1=on
Return value
- This call does not return a value
SetHoldingRegister
Sets the state of a single holding register.
Parameters
- UINT Address
- Coil Address
- UINT Value
- Analogue Value range 0 - 65535
Return value
- This call does not return a value
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.
Parameters
- This macro has no parameters
Return value
SetAnalogueInput
Sets the state of a single analogue input.
Parameters
- UINT Address
- Coil Address
- UINT Value
- Analogue Value range 0 - 65535
Return value
- This call does not return a value
Initialise
Starts up the UART to allow communications and initialises the states of the various
Modbus Coils, Inputs and Registers to 0.
Parameters
- This macro has no parameters
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
Slave Address
This property is of type Unsigned integer and can be referenced with the variable name SlaveAddress.
No additional information
Reply Delay
This property is of type Unsigned integer and can be referenced with the variable name ReplyDelay.
Delay in micro seconds to wait before transmitting a reply
BaudByteDelay
This property is of type Unsigned integer and can be referenced with the variable name BaudByteDelay.
No additional information
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.
Starting Address
This property is of type Unsigned integer and can be referenced with the variable name StartAdrCoil.
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
This property is of type Unsigned integer and can be referenced with the variable name NumAdrCoil.
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.
Starting Address
This property is of type Unsigned integer and can be referenced with the variable name StartAdrDI.
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
This property is of type Unsigned integer and can be referenced with the variable name NumAdrDI.
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.
Starting Address
This property is of type Unsigned integer and can be referenced with the variable name StartAdrAI.
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
This property is of type Unsigned integer and can be referenced with the variable name NumAdrAI.
Specifies how many 16-bit analogue inputs are available on the slave.
Each address consumes two RAM Bytes.
Starting Address
This property is of type Unsigned integer and can be referenced with the variable name StartAdrReg.
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
This property is of type Unsigned integer and can be referenced with the variable name NumAdrReg.
Specifies how many 16-bit holding registers are available on the slave.
Each address consumes two RAM Bytes.
