Technical data

Table Of Contents
SFCs for Distributed I/Os or PROFINET IO
System Software for S7-300/400 System and Standard Functions - Volume 1/2
16-22
A5E00709327-01
16.6 Writing Consistent Data to a DP Standard
Slave/PROFINET IO Device with SFC 15 "DPWR_DAT"
Data Consistency
Refer to the section: Overview of S7 Communication and S7 Basic Communication
– Data Consistency .
Purpose of SFC 15
You require SFC 15 "DPWR_DAT" because you can only write a maximum of four
continuous bytes using the transfer instructions that access the I/Os or the process
image input table.
Note
If required, you can also read consistent data via the process image of the inputs.
To determine whether the CPU supports this functionality, refer to the "S7-300
Programmable Controller, Hardware and Installation" manual.
All S7-400 CPUs support this functionality.
!
Caution
When using SFC 15 "DPWR_DAT", avoid accessing I/O areas that have process
image partitions with OB6x connections (clocked interrupts) assigned to them.
Description
With SFC 15 "DPWR_DAT" (write consistent data to a DP standard slave), you
transfer the data in RECORD consistently to the addressed DP standard
slave/PROFINET IO device and, if required, to the process image (namely if you
have configured the respective address area of the DP standard slave as
consistency range in a process image):
S7-300 Programmable Controller, Hardware and Installation
ET 200S Interface Submodule, IM151-7 CPU
Base Submodule BM147CPU
For S7-400 CPUs the maximum length is 32 bytes.
The data is transferred synchronously, in other words, on completion of the SFC,
the write job is also completed.
The source area must have the same length as you configured for the selected
module with STEP 7.