Tuesday, March 27, 2012

What is Compact Flash ?

CF card (Compact Flash) at first is a kind of data memory device of portable electronic equipment. As a kind of memory device, it uses flash memory revolutionarily. SanDisk produces it firstly in 1994 and made relatively standard. At present, the physical format of it has been taken by many devices.

By the appearance the CF card can be devided into two kinds: CF I and later CF II card. By the speed it can be devied into CF card, high speed CF card (CF+CF 2.0 standard). Higher speed CF3.0 standard is used in 2005. CF II card slot was mainly uses for micro hardware and any other devices.

CF card and Camera Market
CF card is the first flash memory standard competes with earlier and bigger PCMCIA I memory cardIt is established on the base of Intel NOR flash memory, and then changes to NAND flash memory. CF is the oldest and most successful standard, especially adaptes to professional camera market. It has a longer life and lower unit capacity cost than other storage ways. At the same time it can provide larger capacity with smaller size. 

CF card can be used in PCMCIA card slot directly through adaptor. It can also be connected with all kinds of ports like USB, Firewire, etc through card reader. In addition, because of its bigger size (relative to later minitype memory card), the majority of other fomat memory card can be used on the CF card slot through adaptor, including SD/MMC card, Memory Stick Duo, XD card, and SmartMedia card, etc.

As the storage density of NOR flash memory is lower than newer NAND flash memory, the size of CF card is the biggest among the three kinds of storage card of early 1990s. (The other two are Miniature Card-MiniCard and SmartMedia card.) After that, CF card has changed to use NAND flash memory. Besides, the micro hardware of IBM doesn't use solid-state memory.

CFI card and CFII card
Electrical characteristic of CompactFlash has no differences with PCMCIA-ATA port, but the appearance and size is smaller. Connector is 43 mm wide, and the depth of shell plate is 36 mm, 3.3 mm (CF I card) and 5 mm (CF II card).

CF I card fitted CF II card slot, but CF II card is too thick to fit CF I card slot. The most CF flash memory card is CF I card. 

CF card is thinner and smaller than early PC card (PCMCIA) I. however, the thickness is the same with PC I and II card. CF card is the most successful early memory card. It is more popular than Miniature Card, SmartMedia card, and PC I card. While applying in small size equipments, SmartMedia card is the main competitor of CF card for some time. By the market penetration rate, it has once surpassed CF card. However, the superiority of SmartMedia would end with the coming up of new system memory card (about 2002-2005). The memory card system come up from the end of 1990s to early 2000s (for example SD/MMC, all kinds of Memory Stick, XD-picture card, etc.) have a fierce competition. The new memory card is several times samller than CF card. To some extent it is bigger than the differences between CF card and PC card. The new system will dominate the PDA, mobile phone, and consum digital camera, especially mini types.


Anyhow, CF card will continuely be supported by many devices, and still be the main standard of professional digital camera. Among the produced consum digital camera in 2005, a certain amount of them still support CF card. The main features of CF card still are these following points: it gets the biggest MB data with the least cost, it has the biggest capacity than micro memory card, CF II card can use MicroDrive, and it can connect all kinds of micro memory cards through adaptor. At the same time, the adaptor of CF card port memory card is flater than other kinds, because it has no chip set.

CF port is widely used in PDA, notebook, digital camera, and all kinds of devices including desktop. 

To 2005, the capacity size of CF card has enlarged from the minimum 8MB to the maximum 12GB. (Here 1MB equals 1,000,000byte, 1GB equals 1000MB.)
At first CF card uses Flash Memory as memory card, but with the development of it, all kinds of CF standard card without Flash Memory have shown up. Later on CFA has developed the standard of CF+, makes the range of CF card expanse to non-Flash Memory field, including other I/O devices and disc storage, and a newer physical standard Type II .(Microdrive of IBM is the CF card Type II.) Type II is 5 mm thicker than Type I. 

CF card supports both 3.3 and 5 volt voltage. Any CF card can work under these two kinds of voltage. That makes CF card have a wider range of application. The compatibility of CF card still performs at combining Flash Memory with controller which makes the external devices simpler. Different CF card can be read and written by simple facility and there is no need to worry about the compatibility. Especially when upgrading and updating of CF card, it can guarantee the compatibility of older devices.

At the time of first standardization of CompactFlash, even it is the full size hard disc, the capacity of it will not be as large as 4 GB. So the limitation of ATA standard itself is acceptable. However, with the increasing demand of larger capacity of hard disc, the ATA satandard has changed a lot. Even the Flash Memory will exceed the limitation of 4GB. Therefore new CF standard, CF+ (or CF2.0) has been released. It has two obvious changes: data transmission rate has speeded up to 16Mbit/s; the largest capacity can be 137 GB (according to information from CompactFlash association (CFA). CF 3.0 standard which has a 66Mbit/s data transmission rate has been released. The standard also includes some other features.

CF III generation
  Cologne - CF standard has a new third recension. It speeds up transmission rate of port 4 times. The present standard will be combined with FAT32 file system, and support CF card which has 2.2 GB or more capacity.

 The third recension enunciable CF+ and CF standard has used Ultra DMA 33 and Ultra DMA 66 standard (mainly used for IDE HDD), speeding up the data transmission rate from 15MB/s to 66MB/s. DMA (direct memory access) port can reduce the energy consumption of CPU when managing CF card data transmission. According to standardization organization CF association (CFA), high speed PCMCIA ATA storage and I/O model can join in, too. It will speed up the port transmission rate to 25MB/s. 

CF 5.0 card standard
Theoretically 144 million GB. CF card association (CFA) announces the newly passed CF 5.0 version standard. This new standard has upgraded multiple aspects based on CF 4.1. Especially with the fast growing demand of Flash Memory capacity, CF5.0 promots the capacity several times. The same as 137 GB capacity limitation of hard disc a few years ago, because of 28 bit addressing, CF card has a maximum capacity of 137 GB. Therefore CF 5.0 standard has expansed addressing space to 48 bit. Theoretically the maximum capacity has promoted to 144 PB (144,000 TB). That should satisfy users for a long time. Besides, data transmission unit of new standard has promoted from 128KB to 32MB. It has greatly enhanced transmission efficiency. 

CF 5.0 standard supports ATA-6 and ACS-3 standard. Furthermore, it modifys electrical definition of port for improving compatibility. Similar to solid state hard disc SSD, CF5.0 standard adds TRIM function for management of free space and improving performance. Except the fixed standard, CF 5.0 also provids an optioanal feature: "Video Performance Guarantee", aiming at providing QoS function for large amount of HDV data, avoiding frame loss. Through this function CF card intends to enter into the professional video market like superspeed photography.  

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