Addressing the S7-400
3-4 AutomationSystem S7-400 Hardwareand Installation
A5E00850741-01
3.2 How to Determine the Default Address of a Module

Default Addressing

Youdetermine the default address of a module from the number of the slot of the
module in the CR.
The algorithms used to calculate the default address are different for analog and
digital modules.
The following figure shows the numbering of slots in an 18-slot rack. Youcan also
read off theslot numbers directly from the rack.
123456789101112131415161718
123456789101112131415161718

Default Addresses of Digital Modules

On the S7-400, the default addresses for digital modules start from 0 (First slot in
the central rack which is usually occupied by the power supply module) up to 68
(18th slot).
The algorithm used to calculate the default address of a digital module is:
Default address = (slot number - 1) x 4
Example
The default address of a digital module in the 12th slot is as follows:
Default address = (12 - 1) x 4 = 44