B&R 500 Series, Руководство пользователя

Страница: 204 / 253

Accessories • CompactFlash cards
204 Power Panel 500 User's Manual V 1.00
3 CompactFlash cards
3.1 General information
CompactFlash cards are easy-to-exchange storage media. Due to their robustness against
environmental influences (e.g. temperature, shock, vibration, etc.), CompactFlash cards are
ideal for use as storage media in industrial environments.
3.2 Basics
In order to be suited for use in industrial automation, CompactFlash cards must be highly reli-
able. To make this possible, the following is very important
• Flash technology used
• Efficient algorithm for maximizing the lifespan
• Good mechanisms for detecting and fixing errors in the Flash memory
3.2.1 Flash technology
Currently, CompactFlash cards are available with MLC (Multi Level Cell) and SLC (Single Level
Cell) flash blocks.
SLC flash memory has a lifespan that is 10 times longer than MLC, which is why only Com-
pactFlash cards with SLC flash blocks are suited for industrial applications.
3.2.2 Wear leveling
Wear leveling is an algorithm that can be used to maximize the lifespan of a CompactFlash
card. There are three different algorithms:
• No Wear Leveling
• Dynamic Wear Leveling
• Static Wear Leveling
The basic idea behind wear leveling is to distribute data over a broad area of blocks or cells
on the data carrier so that the same areas don't have to be cleared and reprogrammed over
and over again.
3.2.2.1 No Wear Leveling
The earliest CompactFlash cards didn't have an algorithm for maximizing the lifespan. The
lifespan of a CompactFlash card was determined only by the guaranteed lifespan of the flash
blocks.
3.2.2.2 Dynamic Wear Leveling
Dynamic wear leveling makes it possible to utilize unused flash blocks when writing to a file.