Addressing The M7-400 Modules - Siemens SIMATIC S7-400 Hardware And Installation Manual

Assembling the M7-400
8.2

Addressing the M7-400 Modules

Which Modules Can Be Reached Via a Start Address?
Out of the M7-400 modules, only the application modules can be addressed
directly via an address.
The EXM 478 expansion module, ATM 478 AT adapter module and MSM 478
mass storage module cannot be accessed via the S7-400 backplane bus.
Communication between these modules and the CPU is exclusively via the ISA
bus.
Addressing Application Modules
In contrast to the signal modules which have a default address at least in the
central rack, the application modules have no default address.
This means that you must configure the addresses for the application modules in
STEP 7. The procedure can be found in the manual Configuring Hardware and
Communication Connections with STEP 7 V5.0 .
Addressing Interface Submodules
Addresses of interface submodules, which are operated in a module assembly with
an application module, are only visible locally for the corresponding application
module. The CPU can only address the interface submodules that are installed in
the same rack or an expansion rack belonging to the CPU and that can be reached
via the ISA bus. The addresses of these interface submodules must be configured
via STEP 7. There are no default addresses.
Local access of the CPU to interface submodules allocated to an application
module is not directly possible.
However, the interface submodules can be accessed indirectly via programmed
communication between CPU and application module (see also System Software
for M7-300 and M7-400, Program Design Programming Manual ).
Addressing for Operation in the Segmented Rack
If you assemble M7 modules in a CR2 rack with a divided I/O bus (segmented
rack), the same applies to addressing of the application modules and interface
submodules as in a non-segmented rack.
8-4
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S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01