AddReadVar

Adds a read command on an S7 data point to a request. The data point is specified via its absolute address in the S7 Controller.

Syntax

METHOD AddReadVar   : HRESULT
VAR_INPUT
    pVar            : PVOID;
    nByteSize       : WORD;
    nByteOff        : WORD;
    nArea           : E_S7COMM_DATAAREA;
    nDatablock      : WORD;
END_VAR

Return value

Name	Data type	Description
AddReadVar	HRESULT	E_HRESULTAdsErr.NOTINIT = Function block has not been initialized correctly. E_HRESULTAdsErr.BUSY = Request is active E_HRESULTAdsErr.INVALIDDATA = A transfer parameter has been defined incorrectly E_HRESULTAdsErr.INVALIDSIZE = The frame length is greater than the PDU length

Name

Data type

Description

AddReadVar

HRESULT

E_HRESULTAdsErr.NOTINIT = Function block has not been initialized correctly.

E_HRESULTAdsErr.BUSY = Request is active

E_HRESULTAdsErr.INVALIDDATA = A transfer parameter has been defined incorrectly

E_HRESULTAdsErr.INVALIDSIZE = The frame length is greater than the PDU length

Inputs

Name	Data type	Description
pVar	PVOID	Address of the target variables in the TwinCAT PLC
nByteSize	WORD	Byte length of the data type to be read from the S7 Controller
nByteOff	WORD	Byte offset in the S7 Controller
nArea	E_S7COMM_DATAAREA	S7 data area
nDatablock	WORD	ID of the data block. Is only sent if E_S7COMM_DATAAREA.DATA_BLOCKS is used as the data area.

Requirements

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