Words and Expressions4ferroelectric n. 电 铁电物质；adj. 铁电的 volatile adj. 易失，易变，挥发 bipolar adj. 双极性的 hybrid adj. 混合的router 路由器 dynamic adj. 动力学的，动态的leakage n. 漏，泄漏 refresh v. 刷新，更新offset v. 弥补，抵消，n. 偏移量 mask n. 掩码，掩模，屏蔽lithographic 平版印刷的 erasable adj. 可擦除的，可抹去的programmable adj. 可编程的 ultraviolet (UV) n. 紫外线，adj. 紫外线floppy disk n. 软盘magnetic memories 磁存储器optical memories 光存储器electronic memory 电存储器module format 模块形式flip flop 双稳态多谐振荡器；触发器in parallel 并行的，平行的address pointer 地址指针pay off 带来利益，偿清interface circuitry 接口电路cache memory n. 高速缓冲存储器extra drive 附加驱动data comparator 数据比较器storage cell 存储单元trench capacitor 沟道式电容器RAM Random Access Memory 随机存储器MOS abbr. (Metal-Oxide Semiconductor) 金属氧化物半导体CMOS abbr. (Complementary Metal-Oxide-Semiconductor) 互补金属氧化物半导体SRAM Static Random Access Memory 静态随机存储器DRAM Dynamic Random Access Memory 动态随机存储器ROM Read Only Memory 只读存储器EEPROM Electrically Erasable Programmable ROM 电可擦除可编程只读存储器ECL Emitter Coupled Logic 射极耦合逻辑电路CAM Content Addressable Memory 内容寻址存储器ALU arithmetic logic unit 逻辑运算单元Unit 3 Memory DevicesMemories can be made in mechanical, magnetic, optical, biological and electronic technologies. Examples of magnetic memories are tapes, floppy disks, hard drives and ferroelectricRAMs. Examples of optical memories are CD-ROMs, rewrittable CDs. Electronic memory is used extensively in computer equipment since it is the fastest available. For applications where speed is less important, magnetic and optical technologies are often used.All electronic memory today can be in separate IC format, module format, or can be part of an IC as a macrofunction orcell. In the table below is an overview of some electronic memory. The flip-flop A flip-flop is basically a bi-state circuit in which either a 0 or 1 state can resides. Because of its simplicity, the flip-flop is extremely fast. As a basic element, the flip-flop is used in digital circuits and ICs. A flip-flop will lose its state when the supply voltage is removed. Therefore, it is volatile.The register A register is a set of flip-flops in parallel. Typically a register is 8, 16, 32 or 64 bits wide. Often a register is used to hold data, address pointers, etc. A register is volatile and very fast just like the flip-flop.Table 1. 1TapyPropertiesRead/writeNon-volatileSpeed Cost/bitFlip-flopOne-bit register. Usually used as a basic building block in digital circuits.YesNo Ultra fastVery highRegisterSet of flip-flops holding a byte, word or long word. Used in complex chips such as CPUsYesNoUltra fastVery highSRAMArray of flip-flops that is addressable. Used for temporary storage of data or cacheYesNoVery fasthighDRAMArray of storage cells which is addressable. Used for main computing data storageYesNofastModerate ROMArray of hard-wired cells that is addressable. Programming done at time of chip manufactureYesYesVery fastLow EEPROMElectrically erasable programmable ROM. Number of write cycles is limited.YesYesLow High SRAM (Static Random Access Memory) An SRAM is an array of addressable flip-flops. The array can be configured as such that the data comes out in single bit, 4-bit, 8bit, and etc. format. SRAM is simple, fast and volatile just like the flip-flop, its basic memory cell SRAM can be found on microcontroller boards (either on or off the CPU chip), where the amount of memory required is small and it will not payoff to build the extra interface circuitry for DRAMs. In addition, SRAM is often used as cache because of its high speed.SRAM comes in many speed classes, ranging from several ns for cache applications to 200ns for low power applications. SRAM exists in both bipolar and MOS technology. CMOS technology boasts the highest density and the lowest power consumption. Fast cache memory can be constructed in BiCMOS technology, a hybrid technology that uses bipolar transistors for extra drive. The fastest SRAM memories are available in ECL (Emitter Coupled Logic) bipolar technology. Because of the high power consumption, the memory size is limited in this technology.A special case of SRAM memory is Content Addressable Memory (CAM). In this technology, the memory consists of an array of flip-flops, in which each row is connected to a data comparator. The memory is addressed by presenting data to it (not an address!). All comparators will then check simultaneously if their corresponding RAM register holds the same data. The CAM will respond with the address of the row (register) corresponding to the original data. The main application for this technology is fast look up tables. These are often used in network routers.DRAM (Dynamic Random Access Memory) The