​Memory Cards and Their History in Industrial Applications

Flash memory cards have been around for many years in the consumer world. Today, no digital camera or mobile phone can do without them. But their importance goes far beyond that, as they also have a place in industrial environments and are an essential part of countless applications. In this article, Roger Griesemer, General Manager Storage Solutions at Swissbit AG, takes a closer look at the history of some memory card formats and explains how they differ in industrial applications.

CompactFlash™ Card

In data backup applications, storage media using NAND chips are daunting due to their limited write capacity. Unlike hard disks, the number of writes to flash memory is limited and depends largely on the storage technology used. In the 1990s, when NAND flash memory became more popular and more affordable, people naturally began to seek ways to replace vibration-sensitive magnetic disks with solid-state NAND flash technology. However, due to its limited lifespan, it could only be defined as replaceable and the form factor needed to be much smaller than the 2.5-inch hard disk drives (HDDs) at the time. In the mid-1990s, the CompactFlash card (CF card) with a PATA interface was born.

CompactFlash cards, with capacities measured in megabytes, were quickly adopted by digital camera manufacturers. Soon thereafter, laptops were equipped with CompactFlash card readers, turning CF cards into a portable storage medium. In industrial applications, CompactFlash has shown many advantages, most notably in terms of robustness and resistance to harsh environments. CompactFlash cards have been steadily evolving over the years. Today, it has been updated to version 6.0, and its performance and capacity are still improving.

CFast™ Card

The PATA interface (parallel data transfer) used by CompactFlash cards was later replaced by a serial version (SATA) due to the large number of signal lines in parallel interfaces. The new product was launched in 2008 under the name CFast, and the familiar form factor remained unchanged. However, CFast has been relatively unused in the consumer sector, as SD cards have already dominated the consumer market. But the situation is different for industrial applications, where CFast is widely used, just like its predecessor, the CompactFlash card. Compared with SD cards, CFast has obvious advantages: higher storage capacity; fully physically protected connector interface to prevent accidental contact and contamination; better heat dissipation; use of the same CFC slot and IPC housing; and significantly improved performance.

Just like the switch from PATA to SATA, CFast cards are also evolving, and the adoption of the PCIe interface is imminent. PCIe is the latest interface standard in the storage space. PCIe 3.1 supports data rates up to 4 GB/s, and the new NVMe protocol ensures very low latency from the host driver to the controller firmware.

XQD Card

Likewise, the first field to adopt the XQD format was professional digital cameras. In fact, the XQD standard was defined by some digital camera manufacturers as a memory card with a PCIe interface. As early as 2012, the first camera with a proprietary XQD card was launched. In terms of physical size, the XQD card is between an SD card and a CFast card. However, unlike an SD card, its electrical interface is located on the front and the contacts are protected against accidental touches.

CFexpress Card

XQD originally supported only a single PCIe channel. But it evolved into CFexpress of the CompactFlash Association (CFA) in 2017 and became a published standard. To meet different performance requirements, there are ultra-thin Type A with a single PCIe channel, XQD-compatible Type B supporting 2 channels, and larger Type C with 4 channels. The 2-channel Type B can achieve a data rate of about 1.5 GB/s, which is four times the performance of CFast. Therefore, it can be foreseen that CFexpress cards will be widely used in industrial applications, just like CFast cards.

In addition, it has many of the same advantages as CFast cards: contact protection to prevent accidental touches, a closed housing to protect the device from environmental influences, and safe replacement even in harsh industrial conditions. CFexpress cards are hot-swappable and can be directly replaced during operation, thus reducing downtime of factory equipment.

SD Express

Another product that is competing for the removable storage media market and uses the PCIe interface is the SD Express card. It uses the size and interface of the SD memory card, and has an additional PCIe interface. This allows it to be backward compatible with traditional SD card applications while using advanced PCIe systems. It remains to be seen how widely this standard will be used.

What is the difference between industrial memory cards?

Although memory cards are widely used in both consumer products and industrial environments, in some cases the requirements of the two markets are completely different: For example, thermal management is extremely important in industrial applications. It limits the data rate to ensure that the heat generation remains within the limit without affecting the system performance too much. In addition, NAND flash memory that supports the industrial temperature range of -40℃ to +85℃ should be used, and the flash memory also needs to support cross-temperature (different temperatures when writing and reading).

At the same time, the service life of industrial products is often several times longer than that of consumer products. It is not uncommon for controllers in energy supply systems or railway control systems to be in the field for 20 years, so that even today replacement memory cards still need to be purchased. As a specialist in industrial memory products, Swissbit has been offering specially optimized cards for demanding applications since the days of CompactFlash. Swissbit is one of the drivers of the CFast card market. Swissbit also offers CFexpress cards, which were developed specifically for the embedded market. Swissbit is active not only at the beginning of each generation, but also in products that are entering the legacy phase.

Author: Roger Griesemer, Managing Director Storage Solutions at Swissbit AG.

(Image source: Swissbit)

Swissbit has been supplying products for industrial applications throughout the entire evolution of removable storage media and continues to offer long-term support for legacy systems.

CompactFlash™ cards were originally used as storage for digital photography and later found their way into equipment such as railway control systems and network systems.

Compared to SD memory cards, CFast™ has higher storage capacity, better contact protection to avoid risks such as false touch and contamination, more efficient heat dissipation, and a rugged housing that is easier to use.

Currently, Swissbit has launched the G-20 CFexpress card, which uses cost-effective 3D TLC NAND, and the G-26, which uses 3D pSLC and has high long-term stability.