User-Defined Addressing Of Modules; Addressing Signal Modules - Siemens SIMATIC S7-300 Hardware And Installation Manual

7.3

User-defined addressing of modules

Possible with?
User-defined addressing is only supported by CPUs 315, 315-2 DP, 316-2 DP and
318-2 DP, as well as CPUs 31xC.
User-defined addressing
User-defined addressing means that you can assign an address of your choice to
any module (SM/FM/CP). The addresses are assigned in STEP 7. Here, you
specify the module start address that forms the basis for all other addresses of the
module.
Advantages of user-defined addressing:
• Optimization of the address areas available, since "address gaps" will not occur
between the modules.
• When creating standard software, you can program addresses which are
independent of the respective S7-300 configuration.
7.4

Addressing signal modules

Introduction
This section shows you how to address signal modules. You need this information
in order to be able to address the channels of the signal modules in your user
program.
Addresses of digital modules
The address of an input or output of a digital module consists of a byte address
and a bit address.
e. g. E 1.2
Input
The byte address depends on the module start address.
The bit address is the number printed on the module.
If the first digital module is inserted in slot 4 its default start address is 0.The start
address of any further digital modules is incremented by 4 per slot (see the Figure
in Chapter Slot-based Addressing of Modules).
The figure below shows you how the addresses of the individual channels of a
digital module are obtained.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
Byte address Bit address
Addressing
7-3