Siemens Simatic S7-300 CPU 31xC Series User Manual

Commissioning
8.4 Commissioning the Modules
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
8-11
STOP LED does not flash during the memory reset
What should I do if the STOP LED does not flash during the memory reset or if other LEDs
are lit?
1. You must repeat steps 2 and 3.
2. If the CPU still does not reset memory, evaluate the diagnostic buffer of the CPU.
What happens in the CPU during memory reset?
Table 8-5 Internal CPU events on memory reset
Event Action in CPU
1. The CPU deletes the entire user program in the main memory.
2. The CPU deletes the retentive data.
3. The CPU tests its own hardware.
CPU activities
4. The CPU copies the sequence-relevant content of the MMC (load memory) to the main
memory.
Tip: If the CPU can not copy the MMC and requests a memory reset:
• Remove the MMC
• Reset CPU memory
Read the diagnostic buffer.
Memory contents
after reset
The user program is transferred from the MMC to the main memory again and memory utilization is
indicated accordingly.
Data in the diagnostics buffer.
You can read the diagnostic buffer with the PG (see
STEP 7 Online Help ).
• The MPI parameters (MPI address and highest MPI address, transmission rate, configured MPI
addresses of CPs/FMs in an S7300).
• The same also applies to the CPU 317, if the MPI/DP interface of the CPU was assigned as a
DP interface (PROFIBUS address, highest PROFIBUS address, baud rate, setting as active or
passive interface).
What's left?
Content of elapsed time counter
Special feature: X1 interface parameters (MPI or MPI/DP interface)
The following parameters hold a special position when CPU memory is reset.
• Parameters of interface X1 (MPI parameter or MPI-/DP parameter with MPI-/DP
interfaces).
The table below describes which interface parameters remain valid after a CPU memory
reset.
CPU memory reset ... MPI/DP parameters
with MMC inserted ...the MPI parameters on the MMC or integrated
read-only load memory are valid. If this location
does not contain any parameter data (SDB), the
previously set parameters stay valid.
without micro memory card (MMC) inserted ... are retained and valid.

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)