FB_IPCDiag_ReadParameterPeriodic

The parameters are subdivided into groups. Some of these groups correspond to the modules of the 'Configuration Area' in the MDP. Modules may be instanced several times. Accordingly, a parameter of a multi-instanced module exists several times or has a correspondingly large number of values.

On the other hand, there are list parameters whose identifier already makes this clear. According to the number of list entries, the parameter also exists here several times or has several values.

VAR_INPUT

VAR_INPUT
    bExecute       : BOOL;
    eParameterKey  : E_IPCDiag_ParameterKey;
    nModuleIdx     : USINT := 0;   (* optional module selection for parameters of configuration area; 0:all corresponding modules are read (or rather the first module is read in case of list parameters) *) 
    tPeriod        : TIME := T#60S;               (* set tPeriod >= tTimeout for periodical reading (set 0 for direct execution) *)
    tTimeout       : TIME := DEFAULT_ADS_TIMEOUT; (* ADS communication timeout *)
    sNetId         : T_AmsNetId := '';            (* keep empty '' for the local device *)
END_VAR
VAR_IN_OUT CONSTANT
    fbRegister     : FB_IPCDiag_Register;
END_VAR

bExecute: The function block is called by a positive edge on the input bExecute, if the function block is not already active.

eParameterKey: The parameter to be queried is selected at this input as an enumeration value of the type E_IPCDiag_ParameterKey.
If the parameter is a list parameter, the complete list is read at once and made available.

nModuleIdx: The module index can optionally be specified at this input if the parameter belongs to a module that exists several times.
If the parameter belongs to a multi-existent module and the input nModuleIdx is left at 0, then the parameter values of all module instances are read.
If the parameter is a list parameter, however, then only one module instance can be read.

tPeriod: Specifies the regularity with which the parameter is to be queried. tPeriod must be greater than or equal to tTimeout.

tTimeout: Specifies a maximum time to execute the internal ADS communication.

sNetId: To execute the query on the local device, it is not necessary to specify this input variable. Alternatively, an empty string can be specified. To direct the query to another computer, its AMS Net Id (of type T_AmsNetId) can be specified here.

fbRegister: The instance of FB_IPCDiag_Register must be transferred so that the function block can use the available information for the IPC diagnostic configuration on the target system.
This instance must have been called beforehand. Otherwise an error is output.

VAR_OUTPUT

VAR_OUTPUT
    bValid          : BOOL;     (* read data available (equal IF NOT bBusy AND NOT bError) *)
    bError          : BOOL;
    hrErrorCode     : HRESULT;
    ipErrorMessage  : I_TcMessage;
    nReadParameterValues : USINT;    (* number of read parameter values *)
    nModuleCount         : USINT;    (* number of module instances (configuration area) with the demanded parameter *)
END_VAR

bValid: This output is TRUE if a parameter query takes place and bError is FALSE.

bError: Becomes TRUE as soon as an error situation occurs.

hrErrorCode: Returns an error code if the bError output is set.

ipErrorMessage: Returns detailed information if a bError output is set. The interface pointer used here is always valid (not equal to zero) and is of the type I_TcMessage. In particular, the corresponding error is immediately visible as plain text in the PLC OnlineView.

nReadParameterValues: This output indicates the number of parameter values read. In the case of list parameters, therefore, all list entries are always read automatically and made available.

nModuleCount: This output indicates the number of module instances that contain the selected parameter.
The parameter must originate from the MDP Configuration Area for this. Otherwise, nModuleCount=0.

Methods

After the reading procedure has been successfully completed, the parameter can be copied using one of the following methods.

GetParameter() :

METHOD GetParameter : HRESULT
VAR_INPUT
    pBuffer        : PVOID;    // buffer for parameter with a given size of nParameterSize
    nBufferSize    : UDINT;    // buffer size in bytes (for one or more values)
END_VAR

The GetParameter() method provides easy access to the read parameter. All values are available if the parameter existed several times. In that case, all values are copied at once or, as the case may be, as many values are copied as the specified buffer size can contain. Hence, an ARRAY of the corresponding data type can be used to obtain a complete list.
This is not possible with parameters of the type STRING on account of the different length. If a parameter of the type STRING exists several times, or if a list parameter of the type STRING exists, then a different method must be used to read the other values.

GetParameterByIdx() :

METHOD GetParameterByIdx : HRESULT
VAR_INPUT
    pBuffer          : PVOID;            // buffer for parameter with a given size of nParameterSize
    nBufferSize      : UDINT;            // buffer size in bytes (for one or more values)
    nParameterIdx    : USINT(1..255);    // selection of parameter value (1..nReadParameterValues)
END_VAR

This function is required if the parameter was present several times and individual values are to be copied. The input nParameterIdx specifies which parameter value is to be copied. If it is a list parameter, specify the desired list index there. Specify the module index if it is not a list parameter, but a parameter that had several module instances. Both indices begin with 1.

GetParameterStrings() :

METHOD GetParameterStrings : HRESULT
VAR_INPUT
    pBuffer     : PVOID;    // buffer for parameter with a given size of nParameterSize
    nBufferSize : UDINT;    // buffer size in bytes (for one or more values)
    nStrings    : USINT;    // number of strings to be copied (each string with size=nBufferSize/nStrings)
END_VAR

If the parameter existed several times and represents a character string (STRING) in terms of the data type, this method can be used to copy several character strings at the same time. The input nStrings specifies how many character strings are to be copied. An 'ARRAY[1..nStrings] OF STRING' can serve as a buffer.

Requirements