There’s often confusion around CFast cards, so I’m here to clear that up and share some embedded OEM usage models (note that we just announced an Industrial CFast card with a physical write protect switch).
First, the CFast cards are defined by the CompactFlash Association and are basically a higher speed version of CompactFlash. Length and width are the same as CompactFlash and they are slightly thicker (3.6 vs. 3.3 mm), including the space for the label.
The way they get their performance increase is by employing a SATA interface rather than the older Parallel ATA (PATA) or IDE interface. There’s a special connector just for CFast, so a standard SATA cable won’t fit. A CFast connector needs to be on the embedded OEM design.
The physical write protect switch mentioned earlier offers the embedded OEM designer a couple methods to implement their application requirements. In the first instance, the flash cards are preloaded with content at the factory and no further changes to the data are desired during the life of operation. The write protect switch is then moved to the enabled position, thereby eliminating the possibility of writes. In some cases, tamper-evident tape is placed over the switch and used as a method to verify whether anyone has manipulated the data on the card.
The other popular use model is when high-value data is collected and the risk of loss is substantial. In these cases, the write protect switch will be disabled while collecting data, then enabled to protect this content until it arrives at its final retrieval point.
While the CFast Write Protect Switch isn’t used in mainstream PC applications, it offers a key tool in the arsenal of the OEM designer for niche applications.
Steve Larrivee is VP Sales & Marketing for Cactus Technologies Limited and has over 30 years’ experience in the data storage market, including 10 years with SanDisk and 5 years at Seagate Technology.