Commissioning
7.4 Notes on operation
SIMATIC IPC647C
42 Operating Instructions, 12/2010, A5E02669337-02
Features
The flash drive with CompactFlash card acts just like a standard hard disk. No special driver
software is required to operate the Flash drive.
Although the Flash drive reacts like a hard disk superficially, there are restrictions due to the
limited number of write cycles on Flash memory. The service life of a Compact Flash card
depends on the number of write access to the medium - read accesses have no effect.
To maximize the service life of Compact Flash cards, take care that the writing to the cards
is kept to a minimum.
For example, you can do this by ensuring that:
● Swap files of the operating system and application are not located on the Compact Flash
card.
● Cyclic writing is avoided.
Operating systems such as MS-DOS and Windows XP Embedded allow this, for example.
The Enhanced Write Filter (EWF) can be used with XP Embedded, for example. This
minimized the number of write accesses to the Flash drive or avoids it entirely.
Flash drive functions
A Flash drive or a Compact Flash card consists of Flash memory chips.
An intelligent controller integrated in the flash drive manages the flash memory. This
optimizes the use of the Flash memory to achieve a maximum service life.
The service life of a Flash drive depends in part on the following factors:
● Type of file
Executable files (*.EXE) are usually only written once and stays at the same storage
location.
● The number of writes within a given time (the less the better)
Comparison of Flash drive and hard disk drive service life
Examples of the service life for a Flash drive:
With a "Data logger function", a 4 KB file is written to a 1 GB Compact Flash card every
5 seconds. The cluster size is 4 KB in this case. Due to the file segmentation, the file is
always written to another location on the Compact Flash card.
With this example, the Compact Flash card has a theoretical service of 79.3 years.
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