Siemens S5-155U System Manual page 386

The 460 Analog Input Module
Addressing for cyclic/selective
sampling
9 - 14
However, analog input modules and analog output modules may be
given the same address with cyclic sampling because they are
distinguished by the user program. This is not possible with selective
sampling.
For cyclic sampling, you can address the module in the address range
from 0 to 255, and for selective sampling from 128 to 255. For
selective sampling, you can also use the address range from 0 to 127
after appropriate programming in DB 1 of the user program.
Example:
On an analog input module with start address 160 (IB 160 = input
byte 160), input channel 3 is to be scanned by the program.
Step Action
1 Affix the self-adhesive label with address 160 on the free
field under the addressing switch on the module. ADB 5
and ADB 7 are marked on the label.
2 Press the appropriate rockers of the addressing switch down
on the side marked by a dot on the module cover. Set the
other rockers to the opposite setting. This way sets the start
address of the module.
ADB 5 and ADB 7 results in 2
3 Enter the address 160 + 3 x 2 = 166 in the program for
input channel 3.
5 7
+ 2 = 32 + 128 = 160
System Manual
C79000-B8576-C109-03