Siemens SIMATIC S7 Manual page 41

Example:
Parameterization
of the Memory
Areas
Address Mapping
OPEN MODBUS / TCP communication via CP343-1 and 443-1
2XV9450-1MB00; Manual edition 4.3
data_type_1
db_1
start_1
end_1
data_type_2
db _2
start _2
end _2
data_type_3
db _3
start _3
end _3
data_type_4
db _4
start _4
end _4
data_type_5
db _5
start _5
end _5
data_type_6
db _6
start _6
end _6
data_type_7
db _7
start _7
end _7
data_type_8
db _8
start _8
end _8
The following diagram shows the comparison of the SIMATIC memory area
and the Modbus typical register oriented storage arrangement. The diagram
is based on the above parameterization.
The Modbus addresses printed in black refer to the Data Link Layer, the ones
printed in grey refer to the Application Layer.
The SIMATIC addresses printed in black are the offset in the DB. You can
find additionally the Modbus register numbers printed in grey.
Function Block MODBUSCP
B#16#3 Holding Register
W#16#B DB 11
W#16#1 Start address: 1
W#16#1F4 End address: 500
B#16#3 Holding Register
W#16#C DB 12
W#16#2D0 Start address: 720
W#16#384 End address: 900
B#16#4 Input Register
W#16#D DB 13
W#16#2D0 Start address: 720
W#16#3E8 End address: 1000
B#16#0 Not used
0 0
0 0
0 0
B#16#1 Coils
W#16#E DB 14
W#16#280 Start address: 640
W#16#4E2 End address: 1250
B#16#2 Inputs
W#16#F DB 15
W#16#6A4 Start address:1700
W#16#8FC End address: 2300
B#16#1 Coils
W#16#10 DB 16
W#16#6A4 Start address: 1700
W#16#8FC End address: 2300
B#16#0 Not used
0 0
0 0
0 0
5-13