Yeah. I am kinda hungry and ignorant for knowledge and new ideas, like a child. And I'd love to stay hungry and ignorant for a long time, maybe lifetime, though I don't have that much time or energy as thought, which is really a pity.
Flash memory can be read or programmed one byte or word at a time in a random access pattern.
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·Flash memory comprises cells or transistors made of a thin oxide layer. www.ddhw.com
·The cell has two transistors at its ends called the floating gate and the control gate. These operate on the 0 and 1 value concept.www.ddhw.com
·Applying an electric charge to the circuit runs Read/Write actions. www.ddhw.com
·Flash memory works using the tunneling principle to change the position of electrons in the floating gate. www.ddhw.com
·A charge of 10 to 13 volts is usually applied to the floating gate. Once charged, the electrons in the floating gate move to the other side of the oxide layer and change the charge to negative thus forming a barrier between the control and the floating gate. www.ddhw.com
·The threshold value of the charge regulates the functioning. When the flash memory is blank, then the value is one.
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There are two basic forms of flash memory based on the logic gate: NOR flash and NAND flash. The NOR flash uses two gates and the NAND flash uses tunnel injection for writing and tunnel release for erasing.
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还有, 还有:
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Flash memory
Since the mid-1960s, when the great potential of metal-oxide semiconductors (MOS) technology to lead to high-density and high-performance became known, chip makers were thinking hard of how to solve the main problem associated with the MOS memory concept - its volatility. www.ddhw.com
System (main) memory is called RAM (Random Access Memory) and is most responsible for handling operating and application needs. Unfortunately, RAM loses all data when the system is powered down. Thus, RAM belongs to the so-called Volatile Memory.
Another type of memory is called ROM, or Read Only Memory. ROM has data permanently stored even when the system is off. ROM represents Nonvolatile Semiconductor Memory (NVSM) technology. www.ddhw.com
The first solutions for the volatility problem came in 1967 and in form of the floating gate concept and the metal-nitride-oxide-semiconductor (MNOS) memory device. A UV-erasable Programmable ROM (PROM / EPROM) of 1 Kb became widely available in 1971. In 1983, 16 KB EEPROM were introduced.
There are three types of ROM: PROM (Programmable ROM), EPROM (Erasable PROM), and EEPROM (Electrically Erasable PROM). www.ddhw.com
PROM can not be changed after being recorded once. EPROM allows manufacturer to remove one set of instructions in exchange for another set. EEPROM is upgraded by 'flashing' the chip and is called Flash ROM. This is done with the help of a special software program that stores new data on the chip. The term Flash refers to the fact that the entire content of the memory chip is erased in one step.
Basic principles
The basic operating principle of non-volatile semiconductor memory devices is the storage of electric charges in the gate insulator of a MOSFET. www.ddhw.com
The EPROM was the first NVM that could be electrically programmed by the user and erased later. EPROM devices work on the floating gate cell concept and use (at present) hot-electron injection. EPROM devices are not electrically erasable and require UV light to erase the memory. Both operations - programming and data erasing can be done by the user equipped with EPROM programmer and UV light source.
Flash memory is called so because the entire sections of the microchip are erased at once or (flashed). The erasure is caused by Fowler-Nordheim tunneling. www.ddhw.com
Flash memory is used in the digital cameras and camcorders (still image), digital cellular phones, PC cards for laptop PCs, audio digital recorders, PDAs, GPS, answering machine sets.
Flash memory cards lose power when they are disconnected (removed) from the PC, yet the data stored in it is retained for indefinitely long time or until it is rewritten. www.ddhw.com
160G的ipod 有 160 x 1024^3 x 8(bit) 个存储单元,每个存储单元“困住”1000个电子, 可能增加的最大重量 = 160 x 1024^3 x 8 x 1000 x 9.1 x 10^-31 = 1.3 x 10^-15kg,而 化学分析天平精度为10^-7kg,两者相差8个数量级.
160G的ipod 有 160 x 1024^3 x 8(bit) 个存储单元,每个存储单元“困住”1000个电子, 可能增加的最大重量 = 160 x 1024^3 x 8 x 1000 x 9.1 x 10^-31 = 1.3 x 10^-15kg,而 化学分析天平精度为10^-7kg,两者相差8个数量级.