Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
8-1
8 DPV1 SFBs According to PNO AK 1131
8.1 Reading a Data Record with SFB 52 "RDREC"
Note
The SFB 52 "RDREC" interface is identical to the FB "RDREC" defined in the
standard "PROFIBUS Guideline PROFIBUS Communication and Proxy Function
Blocks according to IEC 61131-3".
Description
With the SFB 52 "RDREC" (read record) you read a data record with the number
INDEX from a DP slave/PROFINET IO device component (module or submodule)
that has been addressed via ID.
Specify the maximum number of bytes you want to read in MLEN. The selected
length of the target area RECORD should have at least the length of MLEN bytes.
TRUE on output parameter VALID verifies that the data record has been
successfully transferred into the target area RECORD. In this case, the output
parameter LEN contains the length of the fetched data in bytes.
The output parameter ERROR indicates whether a data record transmission error
has occurred. In this case, the output parameter STATUS contains the error
information.
Note
If a DPV1 slave is configured using a GSD file (GSD as of Rev. 3) and the DP
interface of the DP master is set to "
S7 compatible
", then data records must not be
read from I/O modules in the user program with SFC 52. The reason is that in this
case the DP master addresses the incorrect slot (configured slot +3).
Remedy: Set the interface for the DP master to "DPV1".