Siemens SIMATIC S7-300 Series Reference Manual page 107

Sample Program
Below you will see a small sample program for the exchange of data between DP
master and DP slave. The addresses used in the example are those from Table
2-5.
In the DP Slave CPU
L 2
T MB 6
L EB 0
T MB 7
L MW 6
T PAW 310
CALL SFC 14
LADDR:=W#16#D
RET_VAL:=MW 20
RECORD:=P#M30.0 Byte 20
L MB 30
L MB 7
+ I
T MW 100
Data Transfer in STOP Mode
The DP-Slave CPU goes into STOP: Data in the CPU's transfer memory are
overwritten with "0", that is, the DP Master reads "0".
The DP Master goes into STOP: Current data in the CPU's transfer memory are
retained and can still be fetched by the CPU.
PROFIBUS address
You cannot set the 126 as the PROFIBUS address for the CPU 31x-2.
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
CPU 31x-2 as DP Master/DP Slave and Direct Communication
Data
pre-processing
in DP slave
Forward data to
DP master
L
T
L
L
+
T
L
+
T
CALL
LADDR:= W#16#0
RECORD:= P#M60.0 Byte
20
RET_VAL:= 22 MW
Receive data
from DP master
Further
processing of
received data
In the DP Master CPU
PEB 222 Further
MB 50 processing of
PEB 223 received data in
B#16#3 the DP master
I
MB 51
10 Data Processing
3 in DP master
MB 60
SFC 15 Send data to DP
slave
2-17