FB_S7CommCyclicRequest

Cyclic processing (read/write) of data points of an S7 communication connection can be configured with the FB_S7CommCyclicRequest function block. The bError output states whether the request was successfully carried out. Any errors occurring at the time of the request are displayed via the output sErrorTxt and nErrorID.

Syntax

Definition:

VAR_INPUT
    bExecute        : BOOL;
    nCycleTimeMs    : UDINT;
END_VAR
VAR_OUTPUT
    bError          : BOOL;
    sErrorTxt       : STRING;
    nErrorId        : WORD;
    bBusy           : BOOL;
    nReceiveCounter : BYTE;
END_VAR

Inputs

Name	Data type	Description
bExecute	BOOL	The function block is executed by a rising edge at this input.
nCycleTimeMs	UDINT	Cycle time to be used in [ms].

Outputs

Name	Data type	Description
bError	BOOL	Switches to TRUE if an error occurs during execution.
sErrorTxt	STRING	Contains the error text in the event of an error.
nErrorId	WORD	Outputs an error code in the event of an error.
bBusy	BOOL	TRUE until the function block has executed a command. As long as bBusy = TRUE, the function block will not accept any new commands.
nReceiveCounter	BYTE	Counter for responses received by the S7 Controller. This can be used to check whether a response was received in the cyclic processing.

Methods

Name	Definition location	Description
AddReadVar	Local	Adds a read command for a particular S7 data point to the request.
AddReadBit	Local	Adds a read command for a particular BIT-type S7 data point to the request.
AddReadString	Local	Adds a read command on a STRING-type S7 data point to a request.
AddReadByteArray	Local	Adds a read command to the request in an optimized manner if several data points located consecutively in the memory of the S7 Controller are to be read.
AddWriteVar	Local	Adds a write command for a particular S7 data point to the request.
AddWriteBit	Local	Adds a write command for a particular BIT-type S7 data point to the request.
AddWriteString	Local	Adds a write command on a STRING-type S7 data point to a request.
AddWriteByteArray	Local	Adds a read command to the request in an optimized manner if several data points located consecutively in the memory of the S7 Controller are to be written.
RemoveRead	Local	Removes a variable from a read request.
RemoveWrite	Local	Removes a variable from a write request.

Requirements

Development environment	Target platform	PLC libraries to be integrated (category group)
TwinCAT v3.1.0	PC or CX (x86, x64)	Tc3_S7Comm (Communication)

Further Information