• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Microcontroller Tips

Microcontroller engineering resources, new microcontroller products and electronics engineering news

  • Products
    • 8-bit
    • 16-bit
    • 32-bit
    • 64-bit
  • Applications
    • Automotive
    • Connectivity
    • Consumer Electronics
    • Industrial
    • Medical
    • Security
  • EE Forums
    • EDABoard.com
    • Electro-Tech-Online.com
  • Videos
    • TI Microcontroller Videos
  • EE Resources
    • DesignFast
    • eBooks / Tech Tips
    • FAQs
    • LEAP Awards
    • Podcasts
    • Webinars
    • White Papers
  • EE Learning Center
    • Design Guides
      • WiFi & the IOT Design Guide
      • Microcontrollers Design Guide
      • State of the Art Inductors Design Guide

NOR flash and NAND flash memory usage trends are evolving

December 5, 2017 By Scott Thornton

Not everyone is familiar with the jargon that experienced engineers and technicians use when they talk about Microcontrollers (MCUs) and memory. NAND and NOR flash memories are used both externally and integrated with MCUs onto System-on-Chips (SoCs) and memory usage trends are evolving around other changes in technology. Both NOR and NAND flash have a place in embedded systems, however.NOR Flash and NAND

Background

Skip this section if you are familiar with MCUs and memory.

MCUs often use external flash memory to store boot code. MCU processors are a computing engine only cannot work without software, which the system holds in non-volatile memory. Non-volatile memory does not lose data when power is gone. Examples of non-volatile memory include flash memory. Random Access Memory (RAM) is the working memory for processors to temporarily store data while executing code. Although RAM is fast, it loses everything whenever it loses power. RAM has evolved over the years, but a common type of RAM in use today is DDR DRAM, which stands for “Double Data Rate Dynamic Random Access Memory.”  You will often hear someone referring to RAM as DDR or DRAM; they are merely identifying the specific type of RAM. You can learn more about various types of memory technology in an earlier post; the following is about NAND and NOR.

Embedded Trends NAND and NOR Flash memory

An MCU chip will boot up, getting boot code from non-volatile memory (often flash memory these days.) For example, new car speedometers use MCUs. The speedometer stores the speedometer’s program code in either on-chip (integrated) or external flash memory. Code-shadowing is the process of placing the code on flash memory and moving it to RAM. The trend these days is leaning more towards using external memory with faster serial interfaces. Most memory is accessed with a serial interface. Recall that a serial interface is a wire (or wires) that establish communication between two digital devices, transmitting and receiving data as a series of voltage pulses.

There are two main types of flash memory where code is stored, and they are NAND flash memory and NOR flash memory. NAND has much more capacity and a higher density than NOR. NAND is commonly available in larger capacities at generally above 1 Gb. (SD Cards and USB drives use NAND memory are found at up to 128 Gb and higher, of course.) NOR flash memory’s top capacity is around 1 Gb. NOR is also byte-addressable, which is why it’s used for code retrieval. NAND works with a block of memory at a time, which means that since NAND gets moved a block at a time, it gets put into temporary memory or cache, and then treated as a byte-addressable memory from there. Trends in embedded memory use are leaning towards NAND because operating systems are getting more substantial with the adoption of Linux and Android into embedded systems. It’s not feasible to put an operating system (OS) in NOR; you either need a specialized OS or a higher density form of memory like NAND. NAND is physically larger than NOR, but for external use with fast interfaces, NAND is worth the size trade-off. Thus, for embedded systems, more companies are code-shadowing from NAND; abandoning NOR flash memory to boot from NAND flash memory. Note that technically, the majority of MCUs do not have operating systems. The above refers to trends in memory usage in the embedded world. NOR flash has been evolving by going to higher densities, but changes in how embedded NOR gets used are mainly seen in faster interfaces, such as going from quad SPI to octal SPI.

NAND and NOR flash memory are both sold as external memory chips that are accessed by an MCU via an interface, which is most often SPI. Integrated chips like Systems-on-Chip can include flash memory on the chip and remove the need for an external memory chip and the interface to access the external memory. For a while, the embedded flash was becoming quite a threat to external memory, but what’s happening recently is as the geometries of silicon chips are getting smaller and smaller on microprocessors. (Silicon geometries are reaching less than 20 nm, and yet the size of a silicon atom is 0.2 nm.) Interest in external NOR flash memory chips is increasing because embedded flash is taking up to 60% of SoC real estate in some cases, which is more of an issue when you have a highly integrated design where an IC needs to be very dense because the application is size-constrained. As an example, Wi-Fi/Bluetooth combo chips, which are used in wearables applications such as smartwatches. In this case, you have a tiny footprint in which to place ICs. Instead of building for width on the wearables and the chips, manufacturers have to go high. They just don’t have the real estate and therefore must combine memory, microprocessor, and the baseband radio. They may not need the density of NAND, but they need the high levels of integration.

You may also like:


  • Memory and functional safety in autonomous vehicles
  • flash
    Flash memory keeps cars connected
  • flash
    Tech refresher: Basics of flash, NAND flash, and NOR flash

Filed Under: Embedded, FAQ, Featured, microcontroller Tagged With: basics, FAQ

Primary Sidebar

DesignFast

Design Fast Logo
Component Selection Made Simple.

Try it Today
design fast globle

EE Training Center Classrooms

EE Classrooms

CURRENT DIGITAL ISSUE

A frequency you can count on There are few constants in life, but what few there are might include death, taxes, and a U.S. grid frequency that doesn’t vary by more than ±0.5 Hz. However, the certainty of the grid frequency is coming into question, thanks to the rising percentage of renewable energy sources that…

Digital Edition Back Issues

Subscribe to our Newsletter

Subscribe to weekly industry news, new product innovations and more.

Subscribe today

RSS Current EDABoard.com discussions

  • DC Motor Speed Control
  • D Flip Flop frequency divider
  • FPGA LVDS with separate clock
  • How do you find the angle made by two isosceles triangles in a kite?
  • Limits of duty cycle for ICM7555 IC?

RSS Current Electro-Tech-Online.com Discussions

  • RF modules which can handle high number of bytes per second
  • we are facing an issue with one-wire communication by using DS2485
  • Are Cross-wind compensation and Road crown compensation functions inputs to LKA function?
  • Component identification.
  • Flickering (candle) LED to trigger 555

Footer

Microcontroller Tips

EE World Online Network

  • DesignFast
  • EE World Online
  • EDA Board Forums
  • Electro Tech Online Forums
  • Connector Tips
  • Analog IC Tips
  • Power Electronic Tips
  • Sensor Tips
  • Test and Measurement Tips
  • Wire and Cable Tips
  • 5G Technology World

Microcontroller Tips

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us
Follow us on Twitter Add us on Facebook Follow us on YouTube  Follow us on Instagram

Copyright © 2022 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy