Initial Power On; Resetting Cpu Memory - Siemens SIMATIC S7-300 Hardware And Installation Manual

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 .
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
Commissioning
8-13