Read
This method reads a specified number of records from a database table with the standard table structure specified by Beckhoff. The standard table structure is used in AutoLog mode and in the FB_DBWriteEvt function block, for example.
Syntax
METHOD Read : BOOL
VAR_INPUT
hDBID: UDINT;
sTableName: T_MaxString;
sDBSymbolName: T_MaxString;
eOrderBy: E_OrderColumn := E_OrderColumn.eColumnID;
eOrderType: E_OrderType := E_OrderType.eOrder_ASC;
nStartIndex: UDINT;
nRecordCount: UDINT;
pData: POINTER TO ST_StandardRecord;
cbData: UDINT;
END_VAR
Inputs
Name | Type | Description |
|---|---|---|
hDBID | UDINT | Indicates the ID of the database to be used. |
sTableName | T_MaxString | Name of the table that is to be read. |
sDBSymbolName | T_MaxString | Symbol name to be read from the standard table structure. |
eOrderBy | E_OrderColumn.eColumnID | Sorting column (ID, timestamp, name or value) |
eOrderType | E_OrderType.eOrder_ASC | Sorting direction (ASC or DESC) |
nStartIndex | UDINT | Indicates the index of the first record to be read. |
nRecordCount | UDINT | Indicates the number of records to be read. |
pData | POINTER TO ST_StandardRecord | Address of the structure array into which the records are to be written. |
cbData | UDINT | Indicates the size of the structure array in bytes. |
Return value
Name | Type | Description |
|---|---|---|
Read | BOOL | Displays the status of the method. Returns TRUE as soon as the method execution is finished, even in the event of an error. |
Sample
VAR
fbPLCDBRead : FB_PLCDBReadEvt (sNetID := '', tTimeout := T#5S);
ReadStruct : ST_StandardRecord;
tcMessage : I_TcMessage;
END_VAR
IF fbPLCDBRead.Read(
hDBID:= 1,
sTableName:= 'MyTable_WithLReal',
sDBSymbolName:= 'MyValue',
eOrderBy:= E_OrderColumn.ID,
eOrderType:= E_OrderType.DESC,
nStartIndex:= 0,
nRecordCount:= 1,
pData:= ADR(ReadStruct),
cbData:= SIZEOF(ReadStruct))
THEN
IF fbPLCDBRead.bError THEN
tcMessage := fbPLCDBRead.ipTcResult;
nState := 255;
ELSE
nState := 0;
END_IF
END_IF
Result in the PLC:
