Siemens S7-400 CPUs utilize specific S7 Memory Cards, primarily RAM-based, to store the user program, data blocks, and configuration. These essential components ensure the reliable operation and data retention of the programmable logic controller (PLC).
Understanding S7-400 Memory Card Types
The S7-400 series CPUs are designed to work with particular memory cards that come in various capacities to suit different application requirements. These cards are crucial for the CPU to load and execute its program. Unlike some modern PLCs that might use SD or CF cards, the S7-400 typically uses dedicated S7 Memory Cards.
- RAM (Random Access Memory) Cards: The most common type for S7-400 CPUs, as indicated by the available options, are RAM-based memory cards. These cards provide fast read/write access and are primarily used for program and data storage. They often require a backup battery on the CPU to retain their contents during power cycles, although the S7-400 CPUs have their own integrated battery backup for this purpose.
Compatible S7-400 Memory Cards
For an S7-400 CPU, you can use a range of S7 Memory Cards, distinguished by their order number and storage capacity. Selecting the correct memory card depends on the size and complexity of your automation project.
The following table details the specific RAM S7 Memory Cards compatible with S7-400 CPUs:
| Order Number | Memory Card Type | Capacity |
|---|---|---|
| 6ES7952-0AF00-0AA0 | S7 Memory Card, RAM | 64KB |
| 6ES7952-1AH00-0AA0 | S7 Memory Card, RAM | 256KB |
| 6ES7952-1AK00-0AA0 | S7 Memory Card, RAM | 1MB |
| 6ES7952-1AL00-0AA0 | S7 Memory Card, RAM | 2MB |
Practical Considerations for Selection
When choosing a memory card for your S7-400 CPU, consider these factors:
- Program Size: The most critical factor is the size of your PLC program. A complex automation project with numerous function blocks, data blocks, and organizational blocks will require a larger memory card.
- Data Storage Needs: If your application involves extensive data logging, recipe management, or large arrays of variables, opt for a higher-capacity card.
- Future Expansion: Always consider potential future expansions of your automation system. It's often prudent to select a card with some overhead capacity to accommodate future program modifications without needing a hardware upgrade.
- CPU Compatibility: While the cards listed are generally compatible with S7-400 CPUs, it's always good practice to consult the specific CPU's technical specifications for any unique memory card requirements or limitations.
For more detailed information on compatible memory cards and CPU specifications, you can refer to official Siemens support resources, such as the Siemens Industry Online Support.
