FUNCTION_BLOCK RDREC
Read Process Data Record (RDREC)
This function block executes an acyclic read of user or system record-data.
The function is invoked when REQ input is equal to TRUE.
The ID parameter identifies the slot or subslot of the Field Device the data record is read from.
The INDEX input of the READ function block contains an integer which identifies the data record to be read, e.g. Profinet Diagnosis- or I&M-Data.
The MLEN parameter specifies the count of bytes which shall be read as an maximum.
The variable given as RECORD parameter shall be at least of MLEN byte.
If the data record is read successfully, the VALID output indicates that the read data record is stored in the RECORD parameter.
The LEN output contains the actual length of the data that has been read in byte.
If an error occurred, the ERROR output indicates an error and the STATUS output contains the error code.
Code-Example: use RDREC to read the diagnosis of a PN-Slave
PROGRAM PLC_PRG
VAR
rdrec : CommFB.RDREC;
buffer : ARRAY[0..255] OF BYTE;
readError : DWORD;
diagReader : ProfinetCommon.DiagnosisDataReader;
channelDiag : ProfinetCommon.ChannelDiagnosisData;
END_VAR
// Read Diagosis-Data:
rdrec.ID := pnDevice.ID; // "pnDevice" is a Profinet slave in the device tree
rdrec.INDEX := TO_INT(ProfinetCommon.DiagnosisRecordIndex.Device); // = 16#F80C --> get all diagnosis for this device
rdrec.MLEN := TO_INT(SIZEOF(buffer));
rdrec.RECORD := ADR(buffer);
rdrec();
IF(rdrec.VALID AND rdrec.REQ) THEN
//here we have valid data
diagReader.InitData(rdrec.RECORD, TO_UINT(rdrec.LEN));
WHILE(diagReader.Read()) DO
; // do something useful with diag-data
END_WHILE
ELSIF(rdrec.ERROR) THEN
readError := rdrec.STATUS; // read service failed
END_IF
rdrec.REQ := rdrec.BUSY; // only read once
InOut:
|
Scope |
Name |
Type |
Comment |
|
Input |
REQ |
BOOL |
Request |
|
ID |
DWORD |
Identifier of a slot / subslot of a Field Device (see: AddressConcept) |
|
|
INDEX |
INT |
Index of the data record |
|
|
MLEN |
INT |
maximum length to be read |
|
|
RECORD |
POINTER TO BYTE |
Read data record |
|
|
Output |
VALID |
BOOL |
New data record received and is valid |
|
BUSY |
BOOL |
FB is busy |
|
|
ERROR |
BOOL |
Error detected |
|
|
STATUS |
DWORD |
Last detected status |
|
|
LEN |
INT |
Length of the read data record |
