Siemens programming the cpu 314c-2dp User Manual

 

 

 

 

 

 

 

   

 

 

 

 

T I A  Training Document

 

Page 9 of 25 

  Module 

Foreword                     Notes                      

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n                      STEP 7 program  

 

Testing 

Introduction 
The memory of the CPU 31xC can be divided into three areas: 

 

 

 

Only with the MMC plugged in is it possible to load user programs and therefore operate the CPU 
31xC  

Load memory 
The load memory is located on a SIMATIC Micro Memory Card (MMC). 
Its size is exactly the same as that of the MMC. It is used for storing code blocks and data blocks as 
well as system data (configuration, connections, module parameters, etc.). 
Blocks that are marked as not being relevant to program execution are exclusively stored in the load 
memory. 
In addition, the complete planning data for a project can be stored on the MMC. 
 

RAM 
The RAM is integrated on the CPU and cannot be expanded. It is used for processing the code and 
processing the data of the user program. The program is executed exclusively in the RAM and the 
system memory.  
Once the MMC has been plugged in, the RAM of the CPU is retentive. 

System memory 
The system memory is integrated on the CPU and cannot be expanded. 
It contains 
- the operands area for clock memories, timers and counters 
- the process images of the inputs and outputs 
- the local data 

A5 

Issue date: 02/2008                                                                                                                          Programming the CPU 314C-2DP