Is the status of an S7-400 CPU after power off/on (without back-up battery) the same as the state after an overall reset?
In the case of power failure or an overall reset (MRES) in non-back-up mode the following memory areas of the S7-400-CPU are reset:
- Dynamic load memory (RAM)
- Main memory
- System memory
All the data that is stored in these areas is lost with the exception of the MPI parameters (e.g. MPI address of the CPU). These remain after a power failure. Thus, in both cases the CPU behaves identically, which means that after a power failure or an overall reset, the CPU still remains able to communicate. After power failure, the only way of starting is a Restart.
In non-back-up mode there are no remanent memory areas.