Four Logic Levels

John

Google "Multi level flash memory"

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

I do it all the time, but not at speed... I use it to set options on a chip:

Option 1, pin grounded Option 2, pin floating Option 3, pin tied to VDD

...Jim Thompson

Commonly used in mask ROM and probably others for many years. See, for example, US 5585297.

It doesn't "square" the amount of information, it multiplies it by

log2(n) = ln(n)/ln(2)

.. where n is the number of logic levels that can be reliably detected over temperature, process variations, noise etc. Best regards, Spehro Pefhany

So, is your pin grounded, or floating, or tied to Vdd?

VLV

My "pin" is hot-wired ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: "skypeanalog" | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

On a sunny day (Wed, 30 Apr 2008 07:09:18 -0700 (PDT)) it happened Robotnik wrote in :

This is not new, and is done in FLASH memory to increase capacity. Intel, are they at 4 analog levels now?

They have this with a thousand or more levels, it's called ANALOG!

Actually, digital transmission schemes like QAM, PAM, etc. use a number of levels and phase of a carrier to form an information symbol. Each symbol corresponds to a digital bit pattern.

For example, in 16-QAM there are four levels and four phases of the carrier. At any given instant in time the level and phase corresponds to one of the

Note that bits are not carried or transmitted. Amplitude and phase of a sine wave is carried. This is just an example many schemes are possible some carrying 8 or more bits per symbol. Eight bits requires a 256 position constellation of phase and amplitude.

What circuitry is required to turn that single input into 2 bits at CMOS levels? Do you use high value resistors to set the floating level or some arrangement of transistors?

Best regards, Spehro Pefhany

Please find the entry for "cross posting" in Wikipedia, read about cross posting and multiple posting, then stop multiple posting.

Inverters sized for thresholds at 1/4 and 3/4 of VDD is one way.

High-value resistors typically (typical 1K/sq available on analog processes).

...Jim Thompson

Or learn how to filter out ALL googlegroups except for those white-listed individuals ;-)

...Jim Thompson

John

I believe I have read that they are working on 16 levels! That would be four bits in 1 cell! The drive for density is relentless!!!

Rick

Has been before at least one or two times..including on the quantum level.

Cheers Terry