SimpleReadCoilInput

SimpleReadCoilInput (FB)

FUNCTION_BLOCK SimpleReadCoilInput

Representation

Evaluation of the actual values for function codes 01 (Read Coils) or 02 (Read Discrete Inputs)

When evaluating the actual values, only the output arxValue must be considered. This is an array with 64 elements of type BOOL (1 - 64 Coils / Inputs).

The specification of the bits to be transmitted is primarily determined by the choice of the function code (eFunctionCode), the start address (wStartAddr) and the desired number of Coils / Inputs (wNumberOfCoils) in the range 1 - 64.

The actual values are available as follows:

The first element arxValue[0] contains the state of the coil with the number wStartAddress The second element arxValue[1] contains the state of the coil with the number wStartAddress + 1 The third element arxValue[2] contains the state of the coil with the number wStartAddress + 2, etc. Unused elements of arxValue are described with FALSE.

Task: Read the actual value of coil 17

Settings: eFunctionCode: ReadFunctionCodesCoilInput.FC01_ReadCoils wStartAddr = 17 wNumberOfCoils = 1

arxValue[0]: Actual value of coil 17 arxValue[1]: FALSE arxValue[2]: FALSE … arxValue[63]: FALSE

CODESYS

InOut:

Scope	Name	Type	Initial	Comment
Input	xEn	BOOL	TRUE	Enable / disable communication (TRUE = enable)
Input	byUnitId	BYTE	0	Device address
Input	xUpdateActual	BOOL	FALSE	Update of actual values (on every rising edge)
Input	xResError	BOOL	FALSE	Reinitialization of the outputs eErrorCodeCom or eErrorCodeDev to the error-free state (on every rising edge)
Inout	ModbusClient	ModbusClientBase		Client of the device
Output	eFunctionCodeFb	ReadFunctionCodesCoilsInputs		Feedback - Modbus function code for the Modbus telegram
Output	wStartAddrFb	WORD		Feedback - Start address of the coils/inputs to be read
Output	wNumberOfCoilsFb	WORD		Feedback - Number of coils/inputs to be read (1 - 64)
Output	arxValue	ARRAY [0 .. 63] OF BOOL		Array with the current coil/input states
Output	xAlarm	BOOL		Collective fault (TRUE = fault)
Output	xAlarmCom	BOOL		Collective fault - communication (TRUE = fault)
Output	eErrorCodeCom	ModbusErrorCode		Error code - communication (0 = no error)
Output	eErrorCodeDev	SIMPLE_READ_COIL_INPUT_ERROR_CODE		Error code - device (0 = no error)
Output	xBusy	BOOL		Communication indicator (TRUE = communication)
Input Const	wNumberOfCoils	WORD	1	Number of coils/inputs to be read (1 - 64)
Input Const	eFunctionCode	ReadFunctionCodesCoilsInputs	ReadFunctionCodesCoilsInputs.FC01_ReadCoils	Modbus function code for the Modbus telegram
Input Const	wStartAddr	WORD		Start address of the coils/inputs to be read
Input Const	tTimeUpdateActual	TIME	TIME#3s0ms	Update interval for the processes influenced by the input xUpdateActual influenced