Is Parallel NOR Flash Too Fast?

By James Malatesta - 2015-05-28

New Internet of Things (IoT) applications, wearable electronic devices, and industrial market segments are driving an increased interest in Parallel NOR Flash due to its nonvolatile, high density, established ecosystem, and proven reliability, and fast speed.

We’ve seen a trend toward lower-density quad SPI NOR devices (< 128Mb) because of their low cost and pin count. We’ve also seen the demand for traditional high-density Parallel NOR (128Mb to 1Gb devices) maintaining a flat to slight upside trend because these devices continue to offer speed and performance advantages over quad SPI.

Many designers  might not be aware that at the high end of the performance spectrum, existing high-performance, low-power  1.8V Parallel NOR, like our G18 (MT28GU) devices, delivers up to 266 MB/s of burst read performance clocked at 133 MHz.  This offers about 4X higher performance than quad SPI and is 3X faster than standard page-mode Parallel NOR. If you consider this fast speed and the ability to multiplex address and data lines that reduce the active pin count by more than 50%, then you have a product that features a low pin count, low voltage, high density, and high-performance code execution.

It’s hard to talk about Parallel NOR without mentioning execute in place (XIP), a term used to represent the system architectural value of executing code and/or data directly from the Flash memory to the host processor versus the alternative used in many QSPI and NAND designs where the Flash code/data is store and download (SnD), where the code is initially downloaded (or shadowed) from the Flash, into the RAM, and executed from the RAM into the host processor.

The ability to run XIP from Parallel NOR provides faster boot up and recovery performance than SnD and also reduces the required RAM size and power since the RAM doesn’t require the additional density for the shadowed code and/or data.

Other less known features of Parallel NOR deserve mentioning. I remember a  few  years ago, when asked if burst read speeds and address-data multiplexing are features that are valued by system designers in the embedded market, the answer was “no.”  But when asked a different way about high performance and low pin count, the response was quite different.

Parallel NOR security features are another topic for another blog. But, these standard and advanced security features were designed specifically to protect the cellular phone industry from security breaches such as unintentional overwrites, malicious attacks, and cloning. All of which are as important as ever when it comes to system design and application protection.

The important thing is that as the industry evolves, NOR Flash is still running strong and offers a wide-range of mature product technologies to choose from across a well-established ecosystem. We’ve been here before in the first generations of cellular communications where speed, high density, small size, and low power were required for a simple, highly reliable non-volatile interfaces. The products never went away, new applications just returned.

Is Parallel NOR Flash too fast? The answer to this question depends on the application and the designer.  However, the fast speed combined with low pin count, low voltage, and high density (versus performance) of G18 (MT28GU) Parallel NOR Flash provides designers with an ideal solution that is ready for the requirements of future applications.

James Malatesta

James Malatesta