Siemens S5-135U/155U System Manual page 328

Digital Input/Output Modules
Example
Digital input module with 8 inputs (IB 23) or
digital output module with 8 outputs (QB 23).
The address is the sum of binary significances set with the individual coding
switches:
Example
Digital input module with 32 inputs (IB 80) or
digital output module with 32 outputs (QB 80).
The address is the sum of binary significances set with the individual coding
switches:
8-16
23 = 1 + 2 + 4 + 16 = 2
On Setting
(Switch Pressed)
IB 23 (or QB 23)
4
80 = 16 + 64 = 2 + 2
On Setting
(Switch Pressed)
IB 80 (or QB 80)
0 1 2 4
+ 2 + 2 + 2
6
System Manual
C79000-G8576-C199-06