Step 7 Program - Siemens 3VF Series Communications Manual

Communication System Manual 3WN6 Circuit-Breakers
There is also another way of changing parameters in the 3WN6 circuit-breaker, i.e. by connecting
suitable devices to the serial interface at the front of the display unit. It is important that the bits for
cyclic reading of the displayed values are set in order that the S5 software and the visualization can
detect these changes (already configured in this example). This guarantees data consistency between
the circuit-breaker and the S5 data management. Changes should only be made via the serial interface
when the corresponding read request bit (as of DW100 in DBAT) is set.
If several windows are used for displaying the circuit-breaker, only the actually displayed values need
to be updated cyclically. Otherwise the performance is compromised.

3.5.4 STEP 7 program

The kernel of the software block is the same as for S5. However, some changes are required for S7
due to the conversion.
1. The data words in the data blocks of S5 must be multiplied by 2 for S7.
2. The initial I/O addresses do not need to be supplied for the FC10 call.
It is necessary to differentiate between the CPU and the CP as DP master, in order to guarantee data
integrity in S7.
In the case of a CPU as master, CALL SFC14 must be performed prior to CALL FC 10. This copies the
valid input data to the flag area (12 bytes). This must be followed by CALL SFC15, which copies the
flag data (12 bytes) to the output area (see S7 example).
In the case of a CP as master, both calls are replaced by CALL "SEND" and CALL "RECEIVE", which
have the same effect.
© Copyright Siemens AG 1998. All rights reserved.
Version 1.0 (05/98) 79