Re: flash memory
mirrorbit/twinflash is essentially another technology wherein charge is trapped not in floating gate but in a ONO layer over gate of transistor.specifically for mirror bit, it is a virtualgnd NOR array but can be tricked to use it as a NAND as well(though not a good idea in my opinion!!) , also they are used as storing two bits(pits of charge) on drain and source side separately,hence are inherently multibit(not multilevel,though newer designs of these types are multilevel as well, look to saifun for reference as they are inventors of this concept).FN tunnelling and Channel hot electron is the mechanism to erase and pgm respectively as in NOR but as pgm is faster with CHE,so can be used with NAND interface as well.