Order Numbers
The order numbers for memory cards are listed in the technical specifications in Chapter 4.
Configuration
The memory card is slightly larger than a credit card and protected by a strong metal casing. It is plugged into a receptacle at the front of the CPU; the end to be inserted is obvious from the design of the memory card.
Grip
Side elevation
Type plate Front elevation
Order numberName of the Memory Card
Figure 1-6 Structure of the Memory Card
Function
The memory card and an integrated memory area on the CPU together form the load memory of the CPU. In operation, the load memory contains the complete user program including comments, symbols, special additional information that permits decompiling of the user program, and all the module parameters (see Chapter 2.1).
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What the Memory Card Contains
The following data can be stored in the memory card:
• User program, that is, blocks (OBs, FBs, FCs, DBs) and system data
• Parameters that determine the behavior of the CPU
• Parameters that determine the behavior of the I/O modules.
• As of STEP 7 V5.1 the Project in Their Entirety in Suitable Memory Cards.
Types of Memory Cards for the S7-400
Two types of memory card are used in the S7-400:
• RAM cards
• Flash cards (FEPROM cards)
Note
Non-Siemens memory cards cannot be used in the S7-400.
What Type of Memory Card Should You Use?
Whether you use a RAM card or a Flash card depends on how you intend to use the memory card.
Table 1-4 Types of Memory Cards
If you ... ...Then
want to store the data in RAM and you want to modify your program during RUN or RUN-P mode,
use a RAM card
want to store your user program
permanently on the memory card, even with power removed (without backup or outside the CPU),
use a Flash card
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RAM Card
you use a RAM card, you must plug this into the CPU to load the user program.
The user program is loaded with the help of the programming device (PG).
You can load the entire user program or the individual parts such as FBs, FCs, OBs, DBs, or SDBs into the load memory in STOP mode or in RUN-P mode.
If you remove the RAM card from the CPU, the information stored on it is lost. The RAM card does not have a built-in backup battery.
If the power supply has a functioning backup battery or if an external backup voltage is supplied to the CPU via the “EXT. BATT.” socket, the contents of the RAM card are retained after switching off the power supply provided the RAM card remains plugged into the CPU and the CPU remains in the rack.
Flash Card
If you use a Flash card, there are two ways of loading the user program:
• Set the CPU to STOP with the mode selector, plug the Flash card into the CPU, and load the user program with
STEP 7 “PLC –> Load User Program to Memory Card”.
• Load the user program into the Flash card in offline mode at the programming device or adapter and then insert the Flash card into the CPU.
You can only load your complete user program with the Flash card. You can load smaller program sections into the integrated load memory on the CPU using the programming device. In the case of larger program changes, you must always reload the Flash card with the complete user program.
The Flash card does not require voltage to store its contents, that is, the
information stored on it is retained even when you remove the Flash card from the CPU or if you operate your S7-400 system without backup (without backup battery in the power supply module or “EXT. BATT.” socket of the CPU).
Which Memory Card Capacity to Use
The capacity of the memory card you use depends on the size of the user program and the additional memory requirement resulting from the use of function modules or communications modules. See the manuals of these modules for details of their memory requirements.
To optimally use the working memory (code and data) your CPU, you should expand the load memory of the CPU with a memory card with at least the same capacity as the working memory.
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Changing the Memory Card
To change the memory card, follow the steps outlined below:
1. Set the CPU to STOP.
2. Remove the plugged in memory card.
Note
If you remove the memory card, the CPU requests a memory reset by flashing the STOP indicator every three seconds. This sequence cannot be influenced by error OBs.
3. Insert a “new” memory card.
4. Perform a memory reset on the CPU.
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