FB_ReadAdsSymByName

The function block FB_ReadAdsSymByName enables reading of any value from another controller using the symbol name.

On a positive edge at the bRead input the function block reads the value of the variable sVarName from the selected ADS device (e.g. PLC). The ADS device is indicated by the AMS-NetId (sNetId) and the AMS Port number (nPort). The value is written into the variable to which nDestAddr points.

The internal mode of operation of the function block can be changed with the aid of the eComMode input:

eComMode := eAdsComModeSecureCom: After each read process, the handle of the PLC variable is released again. This mode should be used when values are exchanged very slowly.
eComMode := eAdsComModeFastCom: As long as the inputs sVarName, sNetID and nPort do not change, the handle of the PLC variable will not be released after each read process. This mode should be used when values are exchanged very frequently.

Inputs

VAR_INPUT
    bRead            :  BOOL;
    sNetId           :  T_AmsNetId;
    nPort            :  T_AmsPort := 851;
    sVarName         :  STRING(255);
    nDestAddr        :  PVOID;
    nLen             :  UDINT;
    tTimeout         :  TIME := DEFAULT_ADS_TIMEOUT;
    eComMode         :  E_AdsComMode := eAdsComModeSecureCom;
END_VAR

Name	Type	Description
bRead	BOOL	The function block reads the content of the variables sVarName of the selected ADS device and writes it to the variable to which the pointer nDestAddr points.

sNetId	T_AmsNetID	AMS-NetId of the ADS device from which the value is to be read.
nPort	T_AmsNetID	AMS Port number of the ADS device from which the value is to be read.
sVarName	STRING(255)	Symbol name of the variable to be read on the selected ADS device (max. 255 characters).
nDestAddr	PVOID	Address of the variable into which the read value is written.
nLen	UDINT	Length of the variable to be read in bytes.
tTimeout	TIME	Time until processing is aborted.
eComMode	E_AdsComMode	Enum used to specify whether the handle of the PLC variable is released again after each read process.

Outputs

VAR_OUTPUT
    bBusy     :  BOOL;
    bError    :  BOOL;
    nErrorId  :  UDINT;
END_VAR

Name	Type	Description
bBusy	BOOL	The transmission is active.
bError	BOOL	An error occurred during the transmission.
nErrorId	UDINT	ADS error number if an error has occurred.

Requirements

Development environment	required TC3 PLC library
TwinCAT v3.1.0	Tc2_DataExchange