The CompactFlash Association was formed in 1995 to introduce and promote, you guessed it, CompactFlash cards. Prior to CompactFlash, the PC Card form factor ruled the flash storage market.
CompactFlash leveraged the standard ATA interface found on some hard drives and PCMCIA (or ATA) cards. A standard interface on a flash device is obvious today, but in the early 1990s it was the small minority of the market. Raw memory and linear flash devices dominated the market at the time. Linear flash devices were made with raw NOR or NAND flash components and the host system required a driver with the intelligence to manage all the memory functions, including translation, wear leveling, defect management, etc.
The problem with the host driver was that it needed to be matched with the specific memory components and vendor of the memory in the device. When the next-generation memory came to market, or a different vendor’s memory was used, new host drivers would have to be installed. This was terrible for interoperability, hence the beauty of a standardized interface such as ATA.
The standardized CompactFlash interface allowed one OEM system design to support any vendor’s compliant CompactFlash card and freed OEM designers to focus on their core competencies instead of detailed flash management. Over the past 20 years, the Industrial Grade CompactFlash card has become a mainstay for embedded OEM designs.
Fast forward to 2008, when the CompactFlash Association introduced a CFast card with an identical length and width as a CompactFlash card, but about 10 percent thicker. The CFast has a SATA electrical interface using a custom connector that’s defined in the spec. As with CompactFlash, there are many CFast connector vendors to integrate into an OEM design.
The advantages of CFast are a simple modular design, freedom from host flash management responsibilities, and a faster interface than CompactFlash cards could offer. An OEM can choose to populate the CFast at time of shipment with the capacity their customers need.
As with all flash storage devices used in embedded applications, a designer should be conscious of what’s inside the CFast card they’re using. For most reliable, long-life applications, I recommend an Industrial CFast card based on SLC NAND flash memory. For applications with short life cycles, and low write endurance needs that won’t be subjected to constant extreme operating temperatures, designers may find a Commercial CFast based on MLC to be adequate for their systems. Note that a more detailed view of industrial flash storage was covered in an earlier post, Industrial-grade flash is important to embedded designs.
Steve Larrivee is the Vice President of Sales and Marketing for Cactus Technologies Limited. He has more than 30 years of experience in the data storage market, including 10 with SanDisk and five with Seagate Technology.