Siemens S5-135U/155U System Manual page 485

Start Address,
For analog output modules ( 8 outputs) only the lowest address (start address)
Subaddress
is set. Other addresses (subaddresses) are decoded on the module.
Note
The start address of an analog module must be a multiple of the double
channel number.
8 channels : 0, 16, 32, 48, ... 240
If one of the outputs (Channel 0 to 7) of a module is to be addressed, the
relevant subaddress must be specified in the program.
The subaddress of the output, based on the start address of the module, is
given by:
Example:
Analog output module with 8 outputs
The address is the sum of the significances set with the individual coding
switches.
A module with 8 outputs (Channel 0 to 7) and start address 160 reserves the
address range from
In this example, the next free address for another module is 176.
Addresses already assigned must not be set again.
System Manual
C79000-G8576-C199-06
Start address + 2 x channel no. = subaddress
160 = 128 + 32 = 2
On Setting
(Switch Pressed)
160 to address 160 + 7 x 2 = 174
Analog Input/Output Modules
7 5
+ 2
IB 160
9-103