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Nv nets with 4 neurons

The quadcore, or 4-Nv net, is by far the most-common variant of Nv net. You will sometimes also hear this circuit referred to as the "Microcore" -- although this term should strictly be used in reference to a "fully dressed" quadcore, complete with sensors and peripheral circuitry. In its "natural state," a quadcore will, at power-up, be saturated (with 2 processes active) -- here, the active inverter(s) are highlighted:

Saturated quadcore animation

In most cases, though, this won't be what you desire -- you'll generally just want a single active process running:

Quadcore animation

Since 4 neurons will enable you to drive two motors in both directions, the most-common use for a quadcore circuit is as the motivating force behind a 2-motor walker. While I've got more information on this use elsewhere, here's an animation showing how this layout works (motor directions are arbitrarily shown by red or green):

Quadcore motor-drive animation

Image Note that in order to build a device on the basis of a quadcore, you need to use Schmitt inverters (since a Schmitt's hysteresis ensures a clean transition). As a result, quadore circuits will generally be built up from 74*14 or 40106 ICs. The same thing holds for more-complex non-suspended microcore variants -- quintcores, hexcores, and the like.

In a 74HC14 microcore, the Schmitt input guarantees a single output transition when a Nv switches, which keeps it out of saturation. On the other hand, a microcore (or 6 Nv or 8 Nv core) made with "vanilla" 74*240 inverters will also "work" but will quickly saturate from noise picked up in the transition region.

For more information...

Ben Hitchcock has his own writeup of quadcores here.

I've got descriptions of a number of quadcore walker circuits here.

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