Siemens SIMATIC S7-1200

Extended instructions
9.3 Distributed I/O (PROFINET, PROFIBUS, or AS-i)
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
385
9.3.2
RDREC and WRREC (Read/write data record)
You can use the RDREC (Read data record) and WRREC (Write data record) instructions
with PROFINET, PROFIBUS, and AS-i.
Table 9- 75 RDREC and WRREC instructions
LAD / FBD
SCL
Description
"RDREC_DB"(
req:=_bool_in_,
ID:=_word_in_,
index:=_dint_in_,
mlen:=_uint_in_,
valid=>_bool_out_,
busy=>_bool_out_,
error=>_bool_out_,
status=>_dword_out_,
len=>_uint_out_,
rec-
ord:=_variant_inout_);
Use the RDREC instruction to read a data
record with the number INDEX from the
component addressed by the ID, such as
a central rack or a distributed component
(PROFIBUS DP or PROFINET IO). As-
sign the maximum number of bytes to
read in MLEN. The selected length of the
target area RECORD should have at
least the length of MLEN bytes.
"WRREC_DB"(
req:=_bool_in_,
ID:=_word_in_,
index:=_dint_in_,
len:=_uint_in_,
done=>_bool_out_,
busy=>_bool_out_,
error=>_bool_out_,
status=>_dword_out_,
rec-
ord:=_variant_inout_);
Use the WRREC instruction to transfer a
data RECORD with the record number
INDEX to a DP slave/PROFINET IO de-
vice component addressed by ID, such as
a module in the central rack or a distrib-
uted component (PROFIBUS DP or
PROFINET IO).
Assign the byte length of the data record
to be transmitted. The selected length of
the source area RECORD should, there-
fore, have at least the length of LEN
bytes.
1
STEP 7 automatically creates the DB when you insert the instruction.
2
In the SCL examples, "RDREC_DB" and "WRREC_DB" are the names of the instance DBs.