Profibus - SFB52 "RDREC"

S7-315 Master
Sirius Softstarter 3RW44 Profibus DP slave

I want to read
DATA SET 95
ID NO: 603 "Number of starts motor right"

DP address 4
DP ID 192
Diagnostic address 2047




Can anyone explain for me how to get this function block to work? I have tried to read the system manual for the S7-300 and the SFB 52 but I can't figure it out.


CALL "RDREC" , DB52
REQ :=M0.0
ID :=DW#16#4
INDEX :=603
MLEN :=4
VALID :=M0.1
BUSY :=M0.2
ERROR :=M0.3
STATUS:=MD2
LEN := ??
RECORD:=MD6

Why have you got "LEN:= ??" when it should be an integer ?
Have yopu called the block and then analysed the STATUS parameter if an ERROR occurs ?

I'm not shure what to put there... "Length of the fetched data to record"

I'll take a guess.

ID shall be the i/o address of the "module" (not the DP node address) as it appears in the HW Config. And it shall be entered as a hex value.

LEN can be any unused word-sized address. It is only for status of how many words was actually transfered.

RECORD shall be an ANY pointer where to put the retrieved data.
So it should be P#M6.0 BYTE 4 if you want the data to arrive in MD6.

Try using SFC 59 RD_REC it works better, I could never get SFB52 to work either.

Here is a real life one that works, this reads the outputs of a Simocode Pro V

CALL "RD_REC"
REQ :=#RD_REC_67
IOID :=B#16#54
LADDR :=#LADDR
RECNUM :=B#16#43
RET_VAL:=#TEMP_RET_VAL
BUSY :=#RD_REC_67_BUSY
RECORD :=P#DB33.DBX0.0 BYTE 4

The temp variables are input variables so I can set the logical address and trigger the read from elswhere. RET_VAL is discarded and BUSY is only used within the block.