Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 22)

Operating and display elements
2.2 Operating and display elements: CPU 31x
CPU 31xC and CPU 31x, Technical data
2-6
Manual, Edition 08/2004, A5E00105475-05
Slot for the SIMATIC Micro Memory Card (MMC)
A SIMATIC Micro Memory Card (MMC) is used as memory module. You can use MMCs as
load memory and as portable storage medium.
Note
These CPUs do not have an integrated load memory and thus require an MMC for
operation.
Mode selector switch
The mode selector switch is used to set the CPU operating mode.
Table 2-3 Positions of the mode selector switch
Position Meaning Description
RUN RUN mode The CPU executes the user program.
STOP STOP mode The CPU does not execute a user program.
MRES CPU memory reset Mode selector switch position with pushbutton function for CPU
memory reset. A CPU memory reset by means of mode
selector switch requires a specific sequence of operation.
Reference
• CPU operating modes: STEP 7 Online Help.
• Information on CPU memory reset: Operating instructions CPU 31xC and CPU31x,
Commissioning, Commissioning Modules, CP Memory Reset by means of Mode Selector
Switch
• Evaluation of the LEDs upon error or diagnostic event: Operating Instructions CPU 31xC
and CPU 31x, Test Functions, Diagnostics and Troubleshooting, Diagnostics with the
help of Status and Error LEDs
Power supply connection
Each CPU is equipped with a double-pole power supply socket. The connector with screw
terminals is inserted into this socket when the CPU is delivered.