Communication
14.6 Communication via fault-tolerant S7 connections
S7-400H
246
System Manual, 03/2012, A5E00267695-11
You have to extend the monitoring time of the connection when you use long
synchronization cables.
Example: If you are operating 5 fault-tolerant S7 connections with a monitoring time of
500 ms and short synchronization cables (up to 10m) and want to convert to long
synchronization cables (10km), you must increase the monitoring time to 1000 ms.
To ensure CIR capability of the fault tolerant system, activate the option "Save connections
prior to loading" in Step7 Netpro.
Programming
Fault-tolerant communication can be implemented on the fault-tolerant CPU and is
implemented by means of S7 communication.
This is possible only within an S7 project/multiproject.
Fault-tolerant communication is programmed in STEP 7 by means of communication SFBs.
Those blocks can be used to transfer data on subnets (Industrial Ethernet, PROFIBUS). The
standard communication SFBs integrated into the operating system offer you the option of
acknowledged data transfer. In addition to data transfer, you can also use other
communication functions for controlling and monitoring the communication peer.
User programs written for S7 connections can also be run for fault-tolerant S7 connections
without program modification. Cable and connection redundancy has no effect on the user
program.
Note
For information on programming the communication, refer to the STEP 7 documentation
(e.g.
Programming with STEP 7).
The START and STOP communication functions act on exactly one CPU or on all CPUs of
the fault-tolerant system (for more details refer to the
System Software for S7-300/400,
System and Standard Functions Reference Manual).
Any disruption of subconnections while communication jobs are active over fault-tolerant S7
connections leads to extended delay times.
NOTICE
Downloading the connection configuration in RUN
If you download a connection configuration during operation, any established connections
could be canceled.
