Siemens SIMATIC S7-1200

Extended instructions
9.3 Distributed I/O (PROFINET, PROFIBUS, or AS-i)
S7-1200 Programmable controller
408 System Manual, V4.2, 09/2016, A5E02486680-AK
9.3.10
Others
9.3.10.1
DPRD_DAT and DPWR_DAT (Read/write consistent data)
Use the DPRD_DAT (Read consistent data) instruction to read one or more bytes of data
consistently, and use the DPWR_DAT (Write consistent data) instruction to transfer one or
more bytes of data consistently. You can use the DPRD_DAT and DPWR_DAT instructions
with PROFINET and PROFIBUS.
Table 9- 88 DPRD_DAT and DPWR_DAT instructions
LAD / FBD
SCL
Description
ret_val := DPRD_DAT(
laddr:=_word_in_,
record=>_variant_out_);
Use the DPRD_DAT instruction to read one or more
bytes of data from modules or submodules of one of
the following locations:
• Local base I/O
• DP slave
• PROFINET I/O device
The CPU transfers the data read consistently. If no
errors occur during the data transfer, the CPU enters
the read data into the target area set up by the
RECORD parameter. The target area must have the
same length as you configured with STEP 7 for the
selected module. When you execute the DPRD_DAT
instruction, you can only access the data of one
module or submodule. The transfer starts at the
configured start address.
ret_val := DPWR_DAT(
laddr:=_word_in_,
record:=_variant_in_);
Use the DPWR_DAT instruction to transfer the data
in RECORD consistently to the following locations:
• Addressed module or submodule in the local
base
• DP standard slave
• PROFINET I/O device
The source area must have the same length as you
configured with STEP 7 for the selected module or
submodule.
● The S7-1200 CPU supports consistent peripheral I/O read or write of 1, 2, or 4 bytes. Use
the DPRD_DAT instruction to consistently read and the DPWR_DAT instruction to
consistently write data of lengths other than 1, 2, or 4 bytes.
● You can use these instructions for data areas of 1 or more bytes. If the access is rejected,
error code W#16#8090 results.
● PROFINET supports up to 1024 bytes of consistent data. You do not need to use these
instructions for consistent transfers between the S7-1200 and PROFINET devices.