Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 212)

Appendix
A.1 Information about upgrading to a CPU 31xC or CPU 31x
CPU 31xC and CPU 31x, Technical data
A-6
Manual, Edition 08/2004, A5E00105475-05
A.1.6 Reusing existing hardware configurations
Reusing existing hardware configurations
If you reuse the configuration of a CPU 312 IFM to 318-2 DP for a CPU 31xC/31x, the CPU
31xC/31x may not run correctly.
If this is the case, you will have to replace the CPU in the STEP 7 hardware configuration
editor. When you replace the CPU, STEP 7 will automatically accept all the settings (if
appropriate and possible).
A.1.7 Replacing a CPU 31xC/31x
Replacing a CPU 31xC/31x
When supplied, the CPU 31xC/31x adds a connecting plug to the power supply connector.
You no longer need to disconnect the cables of the CPU when you replace a 31xC / 31x
CPU. Insert a screwdriver with 3.5 mm blade into the right side of the connector to open the
interlock mechanism, then unplug it from the CPU. Once you have replaced the CPU, simply
plug the connecting plug back into the power supply connector.