In This Chapter - Siemens S7-300 Installation Manual

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You must reset CPU memory,
• Before you download a (completely) new user program to the CPU
• If the CPU requests memory reset with its STOP LED flashing at 0.5 Hz
intervals
Table 9-3
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The memory card has been replaced.
RAM error in CPU
Main memory is too small, that is not
all user program blocks on a memory
card can be loaded.
Attempts to load faulty blocks; e.g. if
the wrong instruction was
programmed.
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There are two ways to perform a memory reset on your CPU:
• In this chapter, we will show you how to perform a direct memory reset by
means of the mode selector of your CPU.
• A memory reset by means of your PG can only be performed with STEP 7 in
CPU STOP mode.
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You can find information on how to perform a memory reset of your CPU with a PG
in 67(3  2QOLQH +HOS.
S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01
Possible causes for the CPU memory reset request
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Does not apply to CPU 312 IFM / 314 IFM (314-
5AE0x)
–
CPU with inserted 5 V-FEPROM memory card.
With these causes the CPU requests one
memory reset. After that, the CPU ignores the
contents of the memory card, enters the error
reasons in the diagnostics buffer and goes to
STOP. You can erase or reprogram 5 V FEPROM
Memory Card in the CPU.
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