Siemens S7-1200 System Manual page 78

PLC concepts
4.1 Execution of the user program
Your S7-1200 automation solution can consist of a central rack with the S7-1200 CPU and
additional modules. The term "central rack" refers to either the rail or panel installation of the
CPU and associated modules. The modules (SM, SB, BB, CB, CM or CP) are detected and
logged in only upon powerup.
● Inserting or removing a module in the central rack under power (hot) is not supported.
Never insert or remove a module from the central rack when the CPU has power.
● You can insert or remove a SIMATIC memory card while the CPU is under power.
However, inserting or removing a memory card when the CPU is in RUN mode causes
the CPU to go to STOP mode.
● If you insert or remove a module in a distributed I/O rack (AS-i, PROFINET, or
PROFIBUS) when the CPU is in RUN mode, the CPU generates an entry in the
diagnostics buffer, executes the pull or plug of modules OB if present, and by default
remains in RUN mode.
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WARNING
Safety requirements for inserting or removing modules
Insertion or removal of a module (SM, SB, BB, CD, CM or CP) from the central rack
when the CPU has power could cause unpredictable behavior, resulting in damage to
equipment and/or injury to personnel.
Always remove power from the CPU and central rack and follow appropriate safety
precautions before inserting or removing a module from the central rack.
NOTICE
Risks with removing memory card when CPU is in RUN mode.
Insertion or removal of a memory card when the CPU is in RUN mode causes the CPU
to go to STOP, which might result in damage to the equipment or the process being
controlled.
Whenever you insert or remove a memory card, the CPU immediately goes to STOP
mode. Before inserting or removing a memory card, always ensure that the CPU is not
actively controlling a machine or process. Always install an emergency stop circuit for
your application or process.
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG