[转载]ROM,PROM,EPROM,EEPROM及FLASH存储器的区别（转载大
在微机的发展初期，BIOS都存放在ROM（Read Only
Memory，只读存储器）中。ROM内部的资料是在ROM的制造工序中，在工厂里用特殊的方法被烧录进去的，其中的内容只能读不能改，一旦烧录进去，用户只能验证写入的资料是否正确，不能再作任何修改。如果发现资料有任何错误，则只有舍弃不用，重新订做一份。ROM是在生产线上生产的，由于成本高，一般只用在大批量应用的场合。&
由于ROM制造和升级的不便，后来人们发明了PROM（Programmable
ROM，可编程ROM）。最初从工厂中制作完成的PROM内部并没有资料，用户可以用专用的编程器将自己的资料写入，但是这种机会只有一次，一旦写入后也无法修改，若是出了错误，已写入的芯片只能报废。PROM的特性和ROM相同，但是其成本比ROM高，而且写入资料的速度比ROM的量产速度要慢，一般只适用于少量需求的场合或是ROM量产前的验证。&
EPROM（Erasable Programmable
ROM，可擦除可编程ROM）芯片可重复擦除和写入，解决了PROM芯片只能写入一次的弊端。EPROM芯片有一个很明显的特征，在其正面的陶瓷封装上，开有一个玻璃窗口，透过该窗口，可以看到其内部的集成电路，紫外线透过该孔照射内部芯片就可以擦除其内的数据，完成芯片擦除的操作要用到EPROM擦除器。EPROM内资料的写入要用专用的编程器，并且往芯片中写内容时必须要加一定的编程电压（VPP=12—24V，随不同的芯片型号而定）。EPROM的型号是以27开头的，如27C020(8*256K)是一片2M
Bits容量的EPROM芯片。EPROM芯片在写入资料后，还要以不透光的贴纸或胶布把窗口封住，以免受到周围的紫外线照射而使资料受损。&
鉴于EPROM操作的不便，后来出的主板上的BIOS ROM芯片大部分都采用EPROM（Electrically Erasable
Programmable
ROM，电可擦除可编程ROM）。EPROM的擦除不需要借助于其它设备，它是以电子信号来修改其内容的，而且是以Byte为最小修改单位，不必将资料全部洗掉才能写入，彻底摆脱了EPROM
Eraser和编程器的束缚。EPROM在写入数据时，仍要利用一定的编程电压，此时，只需用厂商提供的专用刷新程序就可以轻而易举地改写内容，所以，它属于双电压芯片。借助于EPROM芯片的双电压特性，可以使BIOS具有良好的防毒功能，在升级时，把跳线开关打至“ON”的位置，即给芯片加上相应的编程电压，就可以方便地升级；平时使用时，则把跳线开关打至“OFF”的位置，防止CIH类的病毒对BIOS芯片的非法修改。所以，至今仍有不少主板采用EPROM作为BIOS芯片并作为自己主板的一大特色。
EPROM、EEPROM都是存储器&
EEROM？还是EPROM？&
EPROM就是Erasable Programmable Read Only
中文含意为“可擦除可编程只读存储器”。它是一种可重写的存储器芯片，并且其内容在掉电的时候也不会丢失。换句话说，它是非易失性的。它通过EPROM编程器进行编程，EPROM编程器能够提供比正常工作电压更高的电压对EPROM编程。一旦经过编程，EPROM只有在强紫外线的照射下才能够进行擦除。为了进行擦除，EPROM的陶瓷封装上具有一个小的石英窗口，这个石英窗口一般情况下使用不透明的粘带覆盖，当擦除时将这个粘带揭掉，然后放置在强紫外线下大约20分钟。主要IC有27XX系列和27CXX系列。&
EEPROM就是electrically erasable, programmable,
read-only&
是一种电可擦除可编程只读存储器，并且其内容在掉电的时候也不会丢失。在平常情况下，EEPROM与EPROM一样是只读的，需要写入时，在指定的引脚加上一个高电压即可写入或擦除，而且其擦除的速度极快！通常EEPROM芯片又分为串行EEPROM和并行EEPROM两种，串行EEPROM在读写时数据的输入／输出是通过2线、3线、4线或SPI总线等接口方式进行的，而并行EEPROM的数据输入／输出则是通过并行总线进行的。
主要IC有28XX系列。
介绍关于闪速存储器有关知识 近年来，发展很快的新型半导体存储器是闪速存储器(Flash
Memory)。它的主要特点是在不加电的情况下能长期保持存储的信息。就其本质而言，Flash
Memory属于EEPROM(电擦除可编程只读存储器)类型。它既有ROM的特点，又有很高的存取速度，而且易于擦除和重写，
功耗很小。目前其集成度已达4MB，同时价格也有所下降。&
由于Flash Memory的独特优点，如在一些较新的主板上采用Flash ROM BIOS，会使得BIOS 升级非常方便。
Memory可用作固态大容量存储器。目前普遍使用的大容量存储器仍为硬盘。硬盘虽有容量大和价格低的优点，但它是机电设备，有机械磨损，可靠性及耐用性相对较差，抗冲击、抗振动能力弱，功耗大。因此，一直希望找到取代硬盘的手段。由于Flash
Memory集成度不断提高，价格降低，使其在便携机上取代小容量硬盘已成为可能。 目前研制的Flash
Memory都符合PCMCIA标准，可以十分方便地用于各种便携式计算机中以取代磁盘。当前有两种类型的PCMCIA卡，一种称为Flash存储器卡，此卡中只有Flash
Memory芯片组成的存储体，在使用时还需要专门的软件进行管理。另一种称为Flash驱动卡，此卡中除Flash芯片外还有由微处理器和其它逻辑电路组成的控制电路。它们与IDE标准兼容，可在DOS下象硬盘一样直接操作。因此也常把它们称为Flash固态盘。
Memory不足之处仍然是容量还不够大，价格还不够便宜。因此主要用于要求可靠性高，重量轻，但容量不大的便携式系统中。在586微机中已把BIOS系统驻留在Flash存储器中。
TF卡（全称TransFlash）是由世界著名存储设备商&
SanDisk开发的一种全球最小闪存卡，尺寸15 x 11 x
1mm，约为SD卡的1/4，和一片指甲差不多大小。在当然按照SanDisk公司的一惯作风，只要和适配器结合使用，就可以使用在标准SD卡设备上。&
得益于其较小的身材，支持TF的设备（比如手机）可以体积上做的和常规差不多大小。而手机界的巨头之一摩托罗拉是此种设备使用最为广泛的企业，在诸如C975、E398、A840、V710、E1000、A1000、V1000等多款手机中都可以使用TF卡。
闪存的英文名称是"Flash
Memory"，一般简称为"Flash"，它也属于内存器件的一种。不过闪存的物理特性与常见的内存有根本性的差异：目前各类DDR、SDRAM或者RDRAM都属于挥发性内存，只要停止电流供应内存中的数据便无法保持，因此每次电脑开机都需要把数据重新载入内存；闪存则是一种不挥发性(Non-Volatile)内存，在没有电流供应的条件下也能够长久地保持数据，其存储特性相当于硬盘，这项特性正是闪存得以成为各类便携型数字设备的存储介质的基础。&
NAND闪存的存储单元则采用串行结构，存储单元的读写是以页和块为单位来进行（一页包含若干字节，若干页则组成储存块，NAND的存储块大小为8到32KB），这种结构最大的优点在于容量可以做得很大，超过512MB容量的NAND产品相当普遍，NAND闪存的成本较低，有利于大规模普及。NAND闪存的缺点在于读速度较慢，它的I/O端口只有8个，比NOR要少多了。这区区8个I/O端口只能以信号轮流传送的方式完成数据的传送，速度要比NOR闪存的并行传输模式慢得多。再加上NAND闪存的逻辑为电子盘模块结构，内部不存在专门的存储控制器，一旦出现数据坏块将无法修正，可靠性较NOR闪存要差。NAND闪存被广泛用于移动存储、数码相机、MP3播放器、掌上电脑等新兴数字设备中。三星、东芝、Renesas和SanDisk是主要的NAND闪存制造商，其中三星电子凭借价格和技术双重优势获得了绝对领先的市场份额，甚至在去年第三季度超过Intel公司成为全球最大的闪存制造商。由于受到数码设备强劲发展的带动，NAND闪存一直呈现指数级的超高速增长，NAND可望在2006年超过NOR成为闪存技术的主导。&
数码闪存卡：主流数码存储介质&
数码相机、MP3播放器、掌上电脑、手机等数字设备是闪存最主要的市场。前面提到，手机领域以NOR型闪存为主、闪存芯片被直接做在内部的电路板上，但数码相机、MP3播放器、掌上电脑等设备要求存储介质具备可更换性，这就必须制定出接口标准来实现连接，闪存卡技术应运而生。闪存卡是以闪存作为核心存储部件，此外它还具备接口控制电路和外在的封装，从逻辑层面来说可以和闪盘归为一类，只是闪存卡具有更浓的专用化色彩、而闪盘则使用通行的USB接口。由于历史原因，闪存卡技术未能形成业界统一的工业标准，许多厂商都开发出自己的闪存卡方案。目前比较常见的有CF卡、SD卡、SM卡、MMC卡和索尼的Memory
Stick记忆棒。&
CF卡（CompactFlash）&
CF卡是美国SanDisk
公司于1994引入的闪存卡，可以说是最早的大容量便携式存储设备。它的大小只有43mm&36mm&3.3mm，相当于笔记本电脑的PCMCIA卡体积的四分之一。CF卡内部拥有独立的控制器芯片、具有完全的PCMCIA-ATA
功能，它与设备的连接方式同PCMCIA卡的连接方式类似，只是CF卡的针脚数多达五十针。这种连接方式稳定而可靠，并不会因为频繁插拔而影响其稳定性。&
CF卡没有任何活动的部件，不存在物理坏道之类的问题，而且拥有优秀的抗震性能，
CF卡比软盘、硬盘之类的设备要安全可靠。CF卡的功耗很低，它可以自适应3.3伏和5伏两种电压，耗电量大约相当于桌面硬盘的百分之五。这样的特性是出类拔萃的，CF卡出现之后便成为数码相机的首选存储设备。经过多年的发展，CF卡技术已经非常成熟，容量从最初的4MB飙升到如今的3GB，价格也越来越平实，受到各数码相机制造商的普遍喜爱，CF卡目前在数码相机存储卡领域的市场占有率排在第二位。&
MMC卡 (MultiMediaCard)&
MMC卡是SanDisk公司和德国西门子公司于1997年合作推出的新型存储卡，它的尺寸只有32mm&24mm&1.4mm、大小同一枚邮票差不多；其重量也多在2克以下，并且具有耐冲击、可反复读写30万次以上等特点。从本质上看，MMC与CF其实属于同一技术体系，两者结构都包括快闪存芯片和控制器芯片，功能也完全一样，只是MMC卡的尺寸超小，而连接器也必须做在狭小的卡里面，导致生产难度和制造成本都很高、价格较为昂贵。MMC主要应用与移动电话和MP3播放器等体积小的设备，而由于体积限制，MMC卡的容量提升较为困难，目前MMC产品以128M容量为主，256MB、512MB主要供应给数码发烧友及特殊用户使用。MMC4.0标准的极速1-2GB
MMC存储卡问世，新标准的MMC多媒体存储卡读取速度最高达到了150倍速（22.5MB/S），而写入速度也达到了惊人的120倍速（18MB/S）。MMC4.0标准同样和原有的MMC存储卡及SD存储卡插槽兼容，可广泛使用在手机、数码相机、掌上电脑、其他移动数字设备等。MMC4.0标准由MMCA多媒体存储卡协会在MMC3.2标准的基础上推出的。&
SD卡（Secure Digital）&
SD卡的英文全称是Secure Digital
Card，意为安全数码卡，它由日本松下公司、东芝公司和美国SanDisk公司共同研制。SD卡仍属于MMC标准体系，SD比MMC卡多了一个进行数字版权保护的暗号认证功能（SDMI规格），故而得名。&
SD卡的尺寸为32mm&24mm&2.1mm，面积与MMC卡相同、只是略厚一些而已。但SD卡的容量比MMC卡高出甚多，SanDisk和松下公司都已推出容量高达1GB的SD卡。不过当前的主流还是64M、128M和256M容量，512MB以上的产品还相当昂贵。读写速度快是SD卡的另一个优点，它的最高读写速度已突破20MB/s、几乎达到闪存读写速度的极限。此外，SD卡还保持对MMC卡的兼容，支持SD卡的插口大多数都可以支持MMC卡。更重要的是，SD卡比MMC卡易于制造，在成本上有不少优势，SD卡得到了广泛应用，在MP3播放器、移动电话、数码相机、掌上电脑及便携式摄像机，目前SD卡接口支持者除了东芝、松下和SanDisk外，还包括卡西欧、惠普、摩托罗拉、NEC、先锋和Palm等公司。&
SM卡（SmartMedia）与xD卡&
SM卡被称为"智能型媒体卡"，尺寸为37mm&45mm&0.76mm，
SM卡的功能较为单一，用户必须使用配有读写及控制功能的专用设备才能对其操作，SM卡规范的升级变化比较大。
以上网友发言只代表其个人观点，不代表新浪网的观点或立场。Free Downloads: Pcmcia Flash Memory Devices
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Publisher: Remo Software, License: Demo, Price: USD $69.00, File Size: 6.9 MB
Platform: Mac
Data card recovery software is great solution to retrieve significant personal records and information from logically damaged USB removable Memory cards in real time. Superior XD picture card data recovery application is finest quality tool that supports and repairs all types of media files such as image files (png, jpeg, jpg, tiff, gif, wmf, emf, exif), video files (3gp, avi, mpeg, mov,...
Category: Utilities / Backup
Publisher: Data card recovery, License: Shareware, Price: USD $45.00, INR2023, File Size: 1.8 MB
Platform: Windows
Recover deleted or lost photo, music and video files from storage Devices like hard drive, Flash Memory cards, USB external drives, ipods .etc. It also recovers digital RAW photo files captured using professional DSLR Cameras. This Media Recovery Software also recovers media files that are lost after formatting a partition having FAT16, FAT32, NTFS, NTFS5, ExFAT file...
Category: Utilities / File & Disk Management
Publisher: Media Recovery Software, License: Demo, Price: USD $49.00, File Size: 19.0 MB
Platform: Windows
Flash Retriever - Flash Media Data Recovery Software is a powerful, easy to use file recovery tool which provides data recovery from damaged or defective Flash Memory Cards. Even if your Flash media has been formatted, Flash Retriever can bring your memories back to life! Accidentally deleted files can also be easily recovered. There are limits to what...
Category: Internet / Browsers
Publisher: DTEC International, License: Demo, Price: USD $130.95, File Size: 432.0 KB
Platform: Windows
Recover data Memory card software salvages missing, damaged files and folders from corrupted/formatted USB Flash Memory card. Memory card picture retrieval utility effectively restores text documents, playlists, epapers etc in few simple steps. Digital storage media file regaining application efficiently compatible with all branded Memory cards including...
Category: Utilities / Backup
Publisher: Recover Data, License: Shareware, Price: USD $45.00, File Size: 1.8 MB
Platform: Windows
Removable media corrupted data recovery software securely retrieves all file, folders and multimedia files from your portable Flash Memory device. Removable media undelete software securely scans your handheld device Memory and let you select the files you wanted to restore. Removable media lost data rescue software supports all USB storage media compact Flash CF,...
Category: Utilities / Backup
Publisher: Data recovery software affiliates, License: Shareware, Price: USD $69.00, File Size: 1.4 MB
Platform: Windows
The Mach X Programmer is a full-featured device programmer that programs a wide range of parts including chips with Flash Memory and One-Time-Programmable Devices (OTP's). High speed programming is accomplished by an internal PIC18 MCU running at 40MHz.
Category: Utilities / Misc. Utilities
Publisher: CCS, License: Shareware, Price: USD $199.00, File Size: 7.3 MB
Platform: Windows