Embedded Software Insight
Over the course of this article, we’ll go through the variations of the protocol used by QSPI NOR Flash devices. We’ll start simple, with the basic SPI protocol then move through the variations to reach some of the more complicated QIO, QPI and DDR variations.
QSPI NAND is a memory technology specifically designed as a direct alternative to its popular cousin, QSPI NOR. But what exactly is QSPI NAND? How does it compare to QSPI NOR? How does it compare to parallel NAND? This is what this article is all about.
In this article we’ll leave the package attributes behind to focus on the internal features of QSPI devices, starting with the memory organization. This article will cover the overall capacity, multi-stack devices as well as the memory map organization units such as pages, blocks and sectors.
In this first article, we’ll go over some important considerations to keep in mind when using a NOR for code shadowing or execute in place, and explain how these considerations may change when using the NOR for data storage with a file system. Then we’ll take a quick look at the hardware characteristics of QSPI NOR devices.
In-depth comparison between NOR and NAND covering aspects of NOR and NAND flash technologies that, in our view, are too often ignored including the impact of the application requirements on the choice of Flash technology.
Let’s explore and compare two different paradigms of flash management commonly used throughout the industry: managed flash and unmanaged flash. Managed flash devices include SD cards, USB flash drives, eMMC and UFS modules — also SSDs, but those are less often seen in embedded systems. These are all NAND-based devices.
This article is the first of an introduction series about flash memory with a focus on embedded systems designs using an embedded file system. A high-level introduction shall we say. Not the kind that takes you straight to the electron and drags you through the depths of quantum physics. No. The purpose of this series … Read more
In this article, we show that TSFS transactions go beyond preserving file-level integrity, and can also be used to enforce coherence across multiple files and directories. To support the discussion, we present a real-life application example and demonstrate how a single additional call to tsfs_commit() is all that is needed to make the code immune to unexpected failures.
In this second article in this series we see how an application can be designed to withstand such unforeseen events, using TSFS transactions. Doing so, we introduce the tsfs_commit() API. We also discuss the write transaction atomicity property, by which applications can be safely designed ignoring potential partial update issues.
This is the first article of a three-part series on fail-safe, storage-related application design using an embedded file system. The first part of the series lays out the fundamental problem of unexpected failures and briefly discusses partial solutions. The second part introduces how a fail-safe transactional file system such as the TREEspan File System (TSFS) … Read more