Technical data

Diagnostics
23.9 Program Measures for Handling Errors
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 515
23.9.9 Insert/Remove Module Interrupt (OB83)
Description
S7-400 CPUs monitor the presence of modules in the central rack and expansion racks at intervals
of approximately 1 second.
After the power supply is turned on, the CPU checks whether all the modules listed in the
configuration table created with STEP 7 are actually inserted. If all the modules are present, the
actual configuration is saved and is used as a reference value for cyclic monitoring of the modules.
In each scan cycle, the newly detected actual configuration is compared with the previous actual
configuration. If there are discrepancies between the configurations, an insert/remove module
interrupt is signaled and an entry is made in the diagnostic buffer and the system status list. In
RUN mode, the insert/remove module interrupt OB is started.
Note
Power supply modules, CPUs, and IMs must not be removed in RUN mode.
Between removing and inserting a module, at least two seconds must be allowed to pass so that the CPU can
detect that a module has been removed or inserted.
Assigning Parameters to a Newly Inserted Module
If a module is inserted in RUN mode, the CPU checks whether the module type of the new module
matches the original module. If they match, the module is assigned parameters. Either the default
parameters or the parameters you assigned with STEP 7 are transferred to the module.
Programming OB83
You must create OB83 as an object in your S7 program using STEP 7. Write the program to be
executed in OB83 in the generated block and download it to the CPU as part of your user program.
You can use OB83, for example, for the following purposes:
• To evaluate the start information of OB83.
• By including system functions SFC55 to 59, to assign parameters to a newly inserted module.
If you do not program OB83, the CPU changes from RUN to STOP when an insert/remove module
interrupt occurs.
You can find detailed information on OBs, SFBs, and SFCs in the corresponding Help on Blocks.