Siemens Automation System S7-400 - Manual (Page 135)

Commissioning
6-7
Automation System S7-400 Hardware and Installation
A5E00850741-01
6.5 Resetting the CPU with the Mode Selector Switch
How to Carry Out a Memory Reset
When you reset a CPU, you place the memories of the CPU in a defined initial
state. The CPU also initializes its hardware parameters and some of the system
program parameters. If you have inserted a Flash card with a user program in the
CPU, the CPU transfers the user program and the system parameters stored on
the Flash card into the main memory after the memory reset.
When Should a CPU be Reset?
You must reset the CPU:
• Before transferring a new, complete user program to the CPU.
• When the CPU requests a reset. Your recognize this request by slow flashing of
the STOP LED at 0.5 Hz.
How to Perform a Memory Reset
There are two ways of resetting the CPU:
• Reset with the mode selector switch
• Reset from the programming device (see STEP 7)
Resetting the CPU with the mode selector is described in the following section.