Siemens SIMATIC S7-300 CPU Data: CPU 315-T-2 DP User Manual

Communication with the S7-300
5.3 Communication services on the MPI/DP interface (X1)
Reference
Further information
• about setting the PG/PC interface for routing can be found in Getting Started
CPU 317T-2 DP: Controlling a SINAMICS S120 in chapter Configuring the PG/PC
Interface
.
• about routing can be found in the
Programming with STEP 7 manual, or directly to the
STEP 7 online help.
• about configuring with
STEP 7 can be found in the Configuring Hardware and
Connections in STEP 7
manual
• fundamentals can be found in the
Communication with SIMATIC Manual.
• about TeleService adapters can be found at Internet website
http://www.ad.siemens.de/support with article ID 14053309 (documentation).
• on SFCs can be found in the
Instruction list , for more details refer to the STEP 7 online
help
or to the System and Standard Functions reference manual.
• on communication can be found in the
Communication with SIMATIC manual.
5.3.8 Data consistency
Properties
A data area is consistent if it can be read or written to from the operating system as a
consistent block. Data exchanged collectively between the stations should belong together
and originate from a single processing cycle, that is, be consistent.
If the user program contains a programmed communication function, for example, access to
shared data with XSEND/ XRCV, access to that data area can be coordinated by means of
the "BUSY" parameter itself.
With PUT/GET functions
For S7 communication functions, such as PUT/GET or write / read via OP communication,
which do not require a block in the user program on the CPU (operating in server mode),
allowances must be made in the program for the extent of the data consistency.
The PUT/GET functions for S7 communication, or for reading/writing variables via OP
communication, are executed at the CPU's scan cycle checkpoint.
In order to ensure a defined process interrupt reaction time, communication variables are
copied consistently in blocks of maximum 160 bytes to/from the user memory at the scan
cycle check point of the operating system. Data consistency is not guaranteed for larger data
areas.
Note
Where defined data consistency is required, the length of communication variables in the
CPU's user program may not exceed 160 bytes.
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
5-13

Siemens SIMATIC S7-300 CPU Data: CPU 315-T-2 DP Specifications

General

Brand	Siemens
Model	SIMATIC S7-300 CPU Data: CPU 315-T-2 DP
Category	Control Unit
Language	English