Flash memory in FH system

By using FEPROMs in a H-system, you have to write it to the FEPROM in each H-CPU.

I am not so font of a FEPROM card in the H-System, if you want to change something it is a hell of a job to get it right in one time.

So you have to load "PLC > Download user program to Memory Card" from STEP7 to one system, then switch over..... and if everything is working well then load the other H-CPU with the new software.... If something is going wrong then the FEPROM of the 1st H-CPU can not be used until the hole H-System may have a shutdown.

If there is one milli-bit different in the 2nd FEPROM then the H-System is finding a difference and it will not start the reserve CPU. So I only use FEPROMs when there is nothing in a distance of several hundreds of kilometer.

Flash cards

A FLASH card can be used for fail-safe backup of the user program and data without a backup battery. You can program the flash card either on the programming device or in the CPU. The flash card also expands the load memory of the CPU.

For detailed information on memory cards, refer to section Structure and Functions of the

Memory Cards (Page 54) in the handbook of the H-System: S7-400H.

When a FLASH Card is inserted, the CPU continues after its memory reset by copying the user program and the system parameters from the FLASH card to RAM.

FLASH card

If you use a Flash card, there are two ways of loading the user program:

● Use the mode selector switch to set the CPU to STOP. Insert the FLASH card into the CPU, and then download the user program to the Flash card in STEP 7 by selecting "PLC > Download user program to Memory Card".

● Load the user program into the Flash card in offline mode on the programming device/programming adapter, and then insert the FLASH card into the CPU. The FLASH card is a non-volatile memory, i.e. its data are retained when it is removed from the CPU or your S7-400 is being operated without backup voltage (without a backup battery in the power supply module or external backup voltage at the "EXT. BATT." input of the CPU). You always download the full user program to a FLASH card.

Safety program on a memory card

If you are using a safety program on a memory card, you must observe the following:

• Before switching the S7 F-System to RUN mode, compare the collective signature of the safety program on the Flash EPROM memory card to the collective signature of the reference data. If necessary, label the memory card with the collective signature.

• In the case of a fault-tolerant S7 FH System, make sure that the memory cards of the redundant F-CPUs are of the same type (RAM or Flash EPROM) and that the same safety program is located on redundant Flash EPROM memory cards.

• Ensure access protection against removal and insertion of memory cards.

ralphtang

Before switching the S7 F-System to RUN mode, compare the collective signature of the safety program on the Flash EPROM memory card to the collective signature of the reference data. If necessary, label the memory card with the collective signature"

Could you explain more detail about that?