editor's blog
Subscribe Now

A New Spin on Logic

Way back in 2008, we took a look at MRAM technology. As a brief review, you may recall that Crocus in particular takes advantage of tunneling magneto-resistance between two magnetic layers. The bottom layer is fixed, or “pinned” and acts as a reference layer. The top one – also referred to as the “free” or “storage” layer – can have its magnetic polarity (or, more accurately, moment) reversed. Selectivity can be improved by engineering the materials so that a current during the write operation will heat the cell and lower the “coercivity” of the material – meaning that you switch that storage layer’s cell without disturbing any other cell. Crocus refers to this as thermally-assisted switching.

With that background (and recommending you to the original article for the details), Crocus has announced what they call a “magnetic logic unit” (MLU). They claim this capability lets them implement a NOR memory architecture, a NAND architecture, or an XOR cell.

They’re still being a bit cautious about the details of how this works, but Crocus’s Barry Hoberman took me though the XOR scenario. Before we can go all the way there, we should take one intermediate step by changing how a cell is read.

Originally, we had a pinned reference layer, and we read the cell by measuring the resistance through the cell. Relatively lower resistance means both layers magnetized alike (or in “alignment”); higher resistance meaning they’re magnetized oppositely (or in “anti-alignment”). So the first step we’re going to take is to remove the pinning. Now the reference layer – also called the “sense” layer, since it helps sense the state of the cell – is magnetically “floating”. Then add some metal lines so that you can magnetize the sense layer as north or south. (To pick arbitrary names for two magnetic states).

To read the cell, first set the sense layer to north and do a resistance read; then, very quickly, switch the sense layer to south and do another read. This is a differential-mode read; whichever resistance is higher establishes the polarity of the storage node.

But here’s where the XOR characteristic comes in: you can ignore the specific northness or southness of the fields. If the two layers – sense and storage – have the same polarity (regardless of what it is), they will run lower resistance; if they have opposite polarity, they’ll have higher resistance. That’s the very definition of the exclusive-OR function (assuming low resistance means 1).

Exactly where all of this will lead product-wise isn’t clear yet. They discuss a number of applications of the NAND and XOR capability, but right now it’s just a technology story. Presumably, staying tuned will give us the rest of the story at some point.

More details in Crocus’s release

Leave a Reply

featured blogs
Jul 12, 2024
I'm having olfactory flashbacks to the strangely satisfying scents found in machine shops. I love the smell of hot oil in the morning....

featured video

Larsen & Toubro Builds Data Centers with Effective Cooling Using Cadence Reality DC Design

Sponsored by Cadence Design Systems

Larsen & Toubro built the world’s largest FIFA stadium in Qatar, the world’s tallest statue, and one of the world’s most sophisticated cricket stadiums. Their latest business venture? Designing data centers. Since IT equipment in data centers generates a lot of heat, it’s important to have an efficient and effective cooling system. Learn why, Larsen & Toubro use Cadence Reality DC Design Software for simulation and analysis of the cooling system.

Click here for more information about Cadence Multiphysics System Analysis

featured paper

Navigating design challenges: block/chip design-stage verification

Sponsored by Siemens Digital Industries Software

Explore the future of IC design with the Calibre Shift left initiative. In this paper, author David Abercrombie reveals how Siemens is changing the game for block/chip design-stage verification by moving Calibre verification and reliability analysis solutions further left in the design flow, including directly inside your P&R tool cockpit. Discover how you can reduce traditional long-loop verification iterations, saving time, improving accuracy, and dramatically boosting productivity.

Click here to read more

featured chalk talk

Autonomous Mobile Robots
Sponsored by Mouser Electronics and onsemi
Robotic applications are now commonplace in a variety of segments in society and are growing in number each day. In this episode of Chalk Talk, Amelia Dalton and Alessandro Maggioni from onsemi discuss the details, functions, and benefits of autonomous mobile robots. They also examine the performance parameters of these kinds of robotic designs, the five main subsystems included in autonomous mobile robots, and how onsemi is furthering innovation in this arena.
Jan 24, 2024