Commissioning
S7-300 Programmable Controller Hardware and Installation
8-16 A5E00105492-01
Structure and Communication Functions, SIMATIC Micro Memory Card (MMC),
section on Formatting an MMC on Memory Reset.
Is the STOP LED not flashing during memory reset?
What do I have to do if the STOP LED is not flashing during memory reset or if
other LEDs are lit (Exception: BATF-LED)?
1. You must repeat steps 2 and 3.
2. If the CPU still does not reset memory, evaluate the diagnostic buffer of the
CPU.
Cold restart with CPU 318-2 DP
With a CPU 318-2DP you can also perform a cold start instead of resetting the
memory.
Cold start means:
• The data blocks in the working memory created by SFC 22 are deleted. The
remaining data blocks have the default value from load memory.
• The process image as well as all timers, counters and memory bits are reset -
irrespective of whether they were configured as retentive.
• OB 102 is processed.
• The process image of the inputs is read before the first instruction in OB1 is
executed.
Step Performing a Cold Start
1. Turn the key to STOP position
2. Turn the key to MRES position Hold the key in this position until the STOP LED
lights up for the second time and remains on (this takes 3 seconds). Then
release the key.
3. Within 3 seconds you must turn the switch to the RUN position.
During Startup the RUN LED flashes at 2 Hz.
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