Storage devices have become an indispensable component of many embedded applications. To select the optimal medium for memory storage, it is essential to consider the specific requirements of your use case. The most prevalent storage mediums for embedded applications are NOR Flash Memory, NAND Flash Memory, SD/MMC Cards, Mass Storage Devices, and RAM.

NOR and NAND flash memory devices are both non-volatile storage mediums, which means they can retain data even without power. MultiMediaCard (MMC) and Secure Digital (SD) cards are flash memory cards that adhere to these standards, and they are also non-volatile memory devices. USB Mass Storage Device Class (USB MSC) is the most commonly used Mass storage device with Cs/FS. USB Drives are also non-volatile memory devices and are recognized by the host device as an external hard drive when connected. RAM storage mediums, on the other hand, are volatile, which means they can't maintain their stored data in the event of a power outage or failure.

When selecting a storage device for embedded applications, it's essential to consider not only the type of storage medium but also the capacity, speed, endurance, and cost. Each storage technology has its own unique characteristics, advantages, and disadvantages. For instance, NOR flash memory is fast, reliable, and ideal for executing code, but it has lower storage capacity and higher cost compared to NAND flash memory. In contrast, NAND flash memory provides higher storage capacity and lower cost but has slower read and write speeds and shorter endurance. By carefully evaluating the specific requirements of your application, you can choose the storage technology that best meets your needs and budget.

NOR Flash Memory

This type of flash memory can execute reads very quickly. These devices tend to be more expensive than the other options. Erase and write operations tend to take longer as well. Due to the higher costs of these devices, the overall capacity of these devices tends to be on the smaller side. NOR devices must write data in large chunks with every write operation. This becomes problematic if your needs do not require writing large quantities of data at a time. Parallel NOR flash utilizes static random-access memory (SRAM) for quick and easy access to the addressable regions of a chip. This provides quick access to every byte stored within it. The overall cost per bit is much higher with NOR flash than with NAND flash. Due to NOR flash’s usage of random-access memory acquisition functionality it is ideal for code execution.

NOR flash tends to be seen in mobile devices, medical devices, robotics, and other devices that benefit from quick code access.

NAND Flash Memory

These flash memory devices are commonly compared to NOR devices. Their read speeds are much slower than your typical NOR device. Due to the layout of NAND circuitry, the memory is accessed serially. These devices can write to a single memory address a byte at a time. NAND is ideal for data storage memory. It is commonly found in devices with requirements for large files frequently being uploaded and overwritten, like MP3 players, USB flash drives, digital cameras, and such.

SD MMC Memory

A MultiMediaCard(MMC) is a form of solid-state storage that utilizes memory card standards. These devices are commonly used for media storage in portable or handheld devices. Traditionally, they can be inserted or removed from the device for ease of access. As of 2018 MMC slots are less commonly available, but eMMC (embedded MMC) cards still find popularity with consumer electronics for integrated storage with portable or embedded devices. They can function as a more cost-effective substitute for a smaller solid-state device as they come with a built-in controller that allows them to appear as a bootable device.

Secure Digital (SD) cards are also non-volatile flash memory. These also utilize the memory card format standard and are commonly used for device storage.

MMCs can be used in SD card slots but not the other way around. SD card will NOT work in designated MMC slots.

Comparison between the two:

Mass Storage Device Class Memory

The idea behind the USB Mass Storage Class (MSC) is to provide a portable storage device that, when plugged into a computer, presents what is interpreted as a built-in hard drive. This is also a form of non-volatile flash memory. USB flash drives are among the more popular forms of removable memory, like MMC and SD cards.

RAM Storage Memory

Of all the storage devices discussed here, this is a volatile memory option. Once the device loses power, this memory is lost. With that, it is obviously not a safe, secure media storage type for storing data long-term. If fast reads and writes are needed, RAM memory is the ideal option.

In Conclusion

These are some of the typical memory devices used for development projects needing a file system or other form of memory storage. Hopefully, this assists in determining the right kinds for your project or provides a nice launching point to further investigate the right type.