Freescale serves up alternative to flash
An electron is not in any particular place. Rather, there is a probability of it appearing somewhere. Like a bookmaker, it's your job to fix the odds so that you get the result you were actually counting on. The quantum particles used in MRAM are persuaded to magically appear on the "wrong side" of a dielectric when a write pulse is applied to the magnetically polarised electrons - and by storing these magnetically polarised electrons, you generate a magnetic field which can be read.
The full explanation (for public consumption) is explained in a white paper from Freescale.
But with Freescale, you never can tell. I know Freescale is capable of wasting an hour of anybody's life by talking about Zigbee technology as being really really useful - and illustrating this by describing electric light bulbs which can be switched on by wireless messages, rather than by ordinary light switches. OK, it's just my opinion, but this is simply a silly idea and one of many technologies which Freescale is prepared to tout as a commercial product, without any real expectation of doing serious business with it.
I suspect it will use Zigbee capability to cross-sell Bluetooth, which solves all the problems Zigbee claims to solve in a more standard manner and for a fraction of the price, but that's just me, and a few other people who are already doing quite well with this tactic.
It wasn't until I started chatting to RFID people that I started getting an enthusiastic response to the MRAM idea. They love it!
And the problem they have is simple: it takes an uncomfortably long time to write data to other non-volatile memory technologies. And it takes power. RFID apps just don't have either to spare. And it's at this point that MRAM suddenly looks magic. To write Flash memory - even fast Flash - takes milliseconds. To write MRAM takes nanoseconds.
So we're looking at the ability to write thousands, even millions, more bits in the same time - and to write it with far less power available.
Of course, that's not the whole story. Any wireless device takes a while to turn on, wake up, and settle down before you can actually start using it, and there again, we're talking milliseconds. So the whole delay involved in using Flash or MRAM storage in an RFID device is not used to write data back to the Oyster card. But (say RFID designers) that makes it even more urgent: the window during which they can write and verify the data written to the card is tiny.
With MRAM, not only can they write a lot more data in that window, but the window is also bigger. The amount of power required to write Flash drops rapidly as the card user moves the card through the field. Users are always being urged to make contact with the pad. There's no actual contact needed, it's just that if you do make contact it takes much longer for you to get in and out of the field, and the voltage generated will be higher.
There's another very important feature, not emphasised in most of the comments: this uses a completely standard CMOS semiconductor technology as its base. The four semiconductor layers required to build up the MRAM cells come on top of standard CMOS layers, which means a non-volatile permanent scratchpad can be incorporated on existing chips.
That does leave one question to which the answer may be wrong, from Freescale's point of view. The question is: "Well, RFID - is that really going to be taking over the world?" and the answer, right now, has to be "nobody can be sure".
The main problem with most RFID applications is that there's an unacceptably high failure rate. In a corporate, administrative environment, it's possible to make incentives for workers, which ensure they patiently ensure that the tags are correctly read (for "incentive" - read, "they get fired if they don't").
But in point of sale applications you're asking your customers to spend extra effort. Take the example of Oyster. In London's underground system, the ticket gates beep once for a successful read, and twice for "there's a problem." You don't have to be Sherlock Holmes to realise that an awful lot of the beeps are double beeps.
London Underground's boss, Transport For London, can mandate the success of Oyster, because it controls pricing. Oyster journeys are cheaper than ticket journeys, not because the margins for the operator are better, but because Mayor Ken Livingstone has decreed that they shall be cheaper. Incentive again; it forces people to use the technology, even if occasionally they can't get into the network and have to go queue at a window to get the error corrected.
You can't run a small coffee-and-sandwich outlet on a street corner like that. If you are going to use RFID, it has to be at least as cheap as any other form of sales transaction (chip and PIN) and as reliable, or your customers simply won't go there.
RFID has yet to pass that test. Don't expect to see any actual four megabit MRAM chips in products this year, or next. And by the time the first products actually appear in commerce, they'll almost certainly be more like 16 megabytes, using smaller-scale silicon geometry, and with prices that make more sense. But if RFID does succeed, this MRAM breakthrough may be what makes that success possible. ®