Commissioning
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
8-13
8.6.2 Initial power on
Prerequisites
• The S7-300 is installed and wired.
• A SIMATIC MMC is inserted in the S7-300 with CPU 31xC.
• The mode selector switch is set to STOP.
Initial Startup of CPUs 31x
Switch on the PS 307 power supply module.
Result:
• The 24 VDC LED on the power supply module is lit.
• The 5 VDC LED on the CPU
– is lit.
– The STOP LED flashes at 2 Hz when the CPU executes an automatic
memory reset.
– The STOP LED is lit after memory reset.
The BATF LED is lit if the backup battery is missing in the CPU (not with
CPU 312 IFM, since not buffered).
Note
If you insert a Memory Card and a backup battery before power is on, the CPU
also requests a memory reset after startup.
Initial Startup of CPUs 31xC
Switch on the PS 307 power supply module.
Result:
• The 24 VDC LED on the power supply module is lit.
• The 5 VDC LED on the CPU
– is lit.
– The STOP LED flashes at 2 Hz when the CPU executes an automatic
memory reset.
– The STOP LED is lit after memory reset.
8.6.3 Resetting CPU memory
When do you reset CPU memory?
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 Possible reasons for this request are listed in the table below .
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