What are the Differences between SPI EEPROMs and SPI Flash Memories?

In embedded systems, a memory device is a physical device that is able to store data that can be used to communicate or perform a certain function. Memory devices can be interfaced through multiple different serial protocols, including SPI, or Serial Peripheral Interface. There are multiple different types of SPI memory devices used in embedded systems, including Flash memory and EEPROMs. In this article, we’ll provide a background on their relationship and a comparison between the two.

EEPROM on circuit board

Example of EEPROM on Circuit Board.  Photo by Micah Elizabeth Scott on Flickr.

Differences Between Flash Memory and EEPROM

SPI Flash memory and EEPROMs are both considered to be nonvolatile memory. Nonvolatile memory means the device is capable of retaining data without the need for constant power, allowing devices to save information even when turned off. They are both electronically writable and erasable memory and are microcontroller-based applications, which means they are used either on or off chip to store information.

While Flash memory and EEPROM devices are both able to store information used in embedded devices, their architecture and operations for reading, writing, and erasing data slightly differ.

EEPROM, which stands for Electrically Erasable Programmable Read-Only Memory,

is a type of memory where data is read, written, and erased at the byte level. Flash memory, on the other hand, which is a type of EEPROM, is architecturally arranged in blocks where data is erased at the block level and can be read or written at the byte level.

What are the Advantages and Disadvantages of Using Flash Memory vs EEPROM?

There are various advantages and disadvantages to using either Flash memory or EEPROM devices:

Because EEPROMs operate their erase functions on a byte-per-byte basis, this increases the time taken to clear and edit the device but it allows developers to edit specific parts if needed. Flash memory is able to erase the device in large chunks of data, which considerably improves the erase speed and allows the device to store information more compactly. However, because of this, it also loses its ability to edit certain bytes, forcing developers to rewrite entire blocks of data upon any changes.

Performing a number of erase and write cycles on a memory device will cause it to eventually degrade over time. One of the advantages of using EEPROM is its improved lifespan. EEPROMs are able to perform up to 1,000,000 erase/rewrite cycles in its lifetime. Depending on the type of Flash memory, Flash devices have a reduced lifespan where most flash products are able withstand around 10,000 to 1,000,000 erase/write cycles before the wear begins to deteriorate the integrity of the storage.

Additionally, in terms of size and cost, Flash memory has a smaller memory cell size than EEPROM and is cheaper to implement.

Flash vs EEPROM Applications

SPI Flash memory, also known as Flash storage, has become widespread in the embedded industry and is commonly used for storage and data transfers in portable devices. Common devices include phones, tablets, and media players, as well as industrial devices like security systems and medical products. Flash memory is particularly useful for static data applications like USB Flash drives.

EEPROMs are also very common in embedded applications, and are frequently used for storing minimal data quantities in computer and electronic systems and devices.

Types of EEPROM and Flash Memory

There are different types of EEPROM and Flash memory. EEPROM supports both serial and parallel access. Serial EEPROMs are interfaced through serial protocols like I2C or SPI. Because of this, it includes a limited number of pins and is able to operate over a minimum number of lines – typically two to four.

Parallel EEPROMs are interfaced using parallel communication using an 8-bit bus and require additional pins to operate – typically up to 28 to 32. While parallel EEPROMs operate faster than serial EEPROMs, serial EEPROMs, including SPI and I2C EEPROMs are preferred due to their simplicity and widespread adoption of I2C and SPI in numerous devices.

There are also multiple types of Flash memory, with NAND and NOR Flash being the most common. Both NOR and NAND Flash offer different advantages for certain applications. NOR Flash offers quicker read speeds and random-access capabilities, while NAND flash is more suitable for quickly writing and erasing data. NAND Flash is more commonly used compared to NOR flash, as it is optimized for high-density storage and is able to achieve a smaller chip size and cost-per-bit due to not having random-access capabilities.

How Total Phase Supports SPI Flash Memory and EEPROM Devices

Total Phase offers multiple host adapter tools that support reading, writing, erasing, and verifying SPI-based Flash memory and EEPROM devices. Depending on the speed and application, embedded system engineers can use the Aardvark I2C/SPI Host Adapter, Cheetah SPI Host Adapter, or the Promira Serial Platform to interface with such memory devices.

The Aardvark I2C/SPI Host Adapter is a general-purpose host adapter capable of signaling up to 8 MHz as an SPI master and up to 4 MHz as an SPI slave. It also can emulate an I2C master or slave device up to 800 kHz.

The Cheetah SPI Host Adapter is designed to support high-speed programming applications, allowing users to signal up to 40 MHz as a master SPI device. It is able to support up to 3 slave selects.  Additionally, it features a pipelined architecture that enables command queuing for maximum throughput.

The Promira Serial Platform is an advanced host adapter tool that is capable of signaling up to 80 MHz as an SPI master and 20 MHz as an SPI slave. It offers multiple other features for advanced programming which include supporting up to 8 slave selects along with support for Dual and Quad I/O.

The Flash Center Software is a software package that allows engineers to quickly erase, program, and verify I2C- and SPI-based EEPROM and Flash memory chips that are interfaced through Total Phase's Promira Serial Platform, Aardvark I2C/SPI Host Adapter, and Cheetah SPI Host Adapter.

Flash Center Software

Unlike other programmers which can take minutes to program a memory device, the Flash Center Software can program the same device in seconds. The Flash Center Software natively supports a wide range of commonly used I2C- and SPI-based Flash memory and EEPROM devices, but it also allows users to easily add new parts if not already supported.

See how to easily program a Flash memory device using a USB to SPI programmer in the Flash Center Software:

Have questions on how our I2C/SPI host adapters can support your Flash memory and EEPROM applications? Please contact us sales@totalphase.com to find out more.