Ram Card; Flash Card; Which Memory Card Capacity To Use - Siemens SIMATIC S7-400H Manual

RAM Card

When you use a RAM card, you have to 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.
When the power supply includes a functioning backup battery or when the CPU is
supplied by an external backup current connected to the "EXT. BATT." socket, the
memory contents of the RAM Card are maintained when the power supply is
switched off as long as the RAM card is inserted in the CPU and the CPU is
inserted in the module 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 into the load memory with the help of the
programming device (PG).
• Load the user program into the Flash card in offline mode at the programming
device 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 power to store its contents, in other words, the
data it contains is maintained when the FLASH card is removed from the CPU or
your S7-400 is being operated without power backup (without a backup battery in
the power supply module or without an external backup current connected to the
"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.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Installation of a CPU 41x-H
4-19