Siemens SIMATIC 427B-HMI/RTX, Руководство пользователя

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User Tasks
2.4 Managing the Enhanced Write Filter
Microbox 427B-RTX/ -HMI/RTX and Panel PC 477B-HMI/ -HMI/RTX
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Manual, 12/2007, A5E01217837-01
2.4 Managing the Enhanced Write Filter
The following Windows XP embedded systems use CompactFlash cards:
●
Microbox PC 420
● Panel PC 477
● Box PC 627
● Microbox PC 427B
● Panel PC 477B
● Box PC 627B
The Enhanced Write Filter (EWF) is a Windows XP embedded utility for protecting a
CompactFlash card. CompactFlash cards allow a limited number of write accesses. When
the Enhanced Write Filter is enabled, Windows XP embedded writes no data to the
CompactFlash card. Instead, the file writes are kept in virtual memory. No difference is
apparent to you when you view file contents. File information appears the same whether it
actually resides on the CompactFlash card or in virtual memory. The difference in file
storage is evident when you reboot the computer or it loses power. All data in virtual memory
is lost, and the computer restarts with the file contents of the CompactFlash card.
You can manage the EWF to maintain data that must persist after a reboot. If you disable the
EWF, all file writes go to the CompactFlash card. This does result in the persistence of all
data after a power loss; however, it causes the most stress over time to the CompactFlash
card.
NOTICE
The Enhanced Write Filter default setting of the D:\ and C:\ drive on the Microbox PCs and
Panel PCs is "Disabled". To protect the CompactFlast card from early failure due to
continuous writes, enable the EWF for the C:\ drive after you have finished the
development of applications on the C:\ drive.
You can also commit all data that is stored in virtual memory to the CompactFlash card at
any point in time, using one of the following commands:
●
commit: The "commit" EWF command writes all data that has accumulated in virtual
memory at that moment in time to the CompactFlash card. The CompactFlash card is not
disabled.
● commitanddisable: The "commitanddisable" EWF command disables the EWF and then
writes all data that has accumulated in virtual memory to the CompactFlash card.
Typically, this command is followed by an enable command to once again protect the
CompactFlash card.
To use the enhanced write filter manager, follow these steps:
1.
Open a command prompt window.
2. Enter "ewfmgr" followed by a drive designation and a command as illustrated.
3. Reboot the computer to make the command take effect.