tag 标签: ram

相关帖子
相关博文
  • 热度 10
    2020-4-27 14:25
    1080 次阅读|
    0 个评论
    单片机就是个小计算机,大计算机少不了的数据存储系统,单片机一样有,而且往往和CPU集成在一起,更加显得小巧灵活。 直到90年代初,国内容易得到的单片机就是8031:不带存储器的芯片,要想工作,还必须外加RAM和ROM,单片机成了3片机...... 现在不同了,大的小的又是51,又是AVR又是STC,还有什么430,PIC等等,都各说各的好,可是谁也不敢说“我不要存储器”。 单片机的数据存储手段 程序存储器ROM 程序存储器里面存放的是单片机的灵魂:工作程序。 小的可能只有1KB,最多只能装1024条8位数据,因为实际指令还有许多2字节,3字节指令,所以它还装不下1024条指令。大的也有128KB的。这些8位数据,要么在工厂里做模子光刻进去,要么一次性的烧写进去。 业余或开发,最多也就是用编程器这么一个特殊工具,把调试成功的机器码装载进去,或者像AVR单片机那样自己花几块钱做一条下载线,把电脑里这些东西灌进去(或许是AVR最吸引人之处)。 它一旦进驻电脑的程序存储器中,除了借助上述装置便不能自由改写,在单片机运行时,只是从其中读出指令或固定的数据,所以给程序存储器一个“只读存储器”的别名,简写为ROM,包括用编程器写紫外线擦除内容的EPROM、用电擦除的EEPROM和现在新兴的FLASH ROM。 一次性写入的ROM,仅用于电路和程序固定的批量产品中,实际工作起来,都是一样的。 为了定位ROM中的数据,每个8位存储单元都有一个固定的“地址”,通常用16进制数表示。例如,对于一个所谓4K的ROM,地址从0000H到0FFFH(即从0000,0001...4095),单片机运行时从哪个地址取数据,完全由程序本身决定,并不要我们干预。 记住,给单片机一通电,它经过一个短暂的复位过程,立即转向ROM的最低地址0000H,在这里面放置的往往是一条“跳转”指令,它从这里一步跳到另一个地址:程序的真正起始地址,例如51机的0080H。 ROM是程序存储器,除了指令外,还包括运行程序必须的某些固定数据,例如:数据表。假如,我们要求在单片机的接口上输出00H到FFH(255)按正弦半波变化的数值,每秒10000次。如果硬要它按照公式一个个计算,对于它来说未免力不从心。可是我们可以把预先计算好的数值存入ROM中,到时候直接取出不是好多了? 又如一个重要的应用:大家一定见过不少单片机的东西上面都有数码显示,那些个数字其实就是用单片机的口线控制数码管的字段电极电位。这些字形也是存放在ROM中的字模表,各个字模和0-9的数字(机器内当然是0000-0101二进制数)对应起来。常见的共阳极7段数码管,必须在阳极加正电,7个阴极都是地电位,才能显示数字"8",数字8对应的显示字码值是二进制数“10000000“(那个1对应的是小数点,高电位不让它显示)。 数据存储器RAM 这是个可以随时存取数据的一块存储器,也就是可以读(取)也可以写(存)的存储器,简称RAM。 现在的单片机里面使用的RAM,属于静态RAM或SRAM,这个和电脑用的内存条有所不同。只要你把数据写入SRAM后,不断电或者不清除掉,这个数据就一直保存在那里。电脑用的是动态RAM,要不断给它加刷新脉冲才能保存数据。 因为单片机处理的信息量比电脑小很多,所以它带的RAM也比较少:从完全不带、带128、256、...1K、2K,到4K,比ROM少多了。 因为实际上RAM只是作为数据临时存放的地方,除非进行图像处理需要存放大量的数据外。一般对于执行较简单任务的单片机,有这么多也够用,如果实在不够用也只能采取外加SRAM如6116、6264等等来扩展。 为了对RAM单元存取8位二进制数,当然也得和ROM一样用“地址”来标示它的具体位置。假如某单片机有1K(1024)RAM,它的地址也是从0000到1024,或16进制数的0000H到03FFH。可见,和ROM的地址是一样的。 会不会混淆不清? 不会,因为读ROM是由单片机的程序指针或转移指令或查表指令进行,而这些指令是不会进入RAM区的;读写RAM是另外的数据传送指令,也不会进入ROM区。这点也是和电脑不同之处,后者程序和数据都在内存条里面,地址不同,如果窜位了就会造成不可预见后果。单片机的这种存储器结构也称为哈佛结构。 RAM在单片机里的用途 RAM在单片机里的用途,主要是存放临时数据。 例如用单片机测温,每秒测1次,显示1分钟的平均值(1分钟更新一次): 我们先通过传感器、放大电路、A/D转换,把温度这个模拟量转变为成比例的二进制数,然后每秒钟1次把数字量通过输入口顺序存入到单片机的RAM中,然后对他们进行两两求和再平均的计算,最后的数值显示出来,然后把这60个存储单元统统写0清除旧数据,下次又是如此循环进行。 结语 另外在单片机里面还有若干寄存器,数量不多但是作用很大,除了暂存数据,还可以交换、加工、传递等等,以及随时记录单片机当前处于什么状态,输入输出口也是作为特殊功能的寄存器存在,具体各有不同,就不是随便说说可以搞清楚的,要看有关书籍了。 - END - 关于造物工场 造物工场立足金百泽超过20年柔性电子制造服务优势,聚焦产品方案和电子工程的设计服务,提供从创意到制造、PCB/PCBA/BOM/元器件等一站式硬件服务。
  • 热度 6
    2014-12-22 19:02
    1453 次阅读|
    0 个评论
    Not typical of me, I was not wearing my happy face several days ago, nor did I perform a single happy dance. The reason for this sad state of affairs started when I arrived at my office at the crack of dawn and powered up the main tower computer that drives the three 28-inch monitors forming my desktop.   Everything seemed to be OK at first. The various applications (Outlook, Firefox, Excel, Word, Visio, Notepad, etc.) appeared to open and run as expected while I was setting up my desktop the way I like it. As soon as I tried to do anything with any of these applications, however, that program immediately locked up. If I subsequently tried to use the ctrl-alt-delete key combination to access the task manager, the entire system locked up and then all three screens went black. Strange to relate, the only thing that continued to work was the lonely cursor associated with my mouse, and there’s not much you can do with a cursor on an otherwise blank screen.   I tried re-booting the machine several times to no avail. There were probably other things I could have tried, but I’d pretty much reached the end of the line. To be honest, this computer has been getting flakier and flakier recently, and I’ve been expecting this day to come for a few months now. We’ve run antivirus and anti-malware tools, and we’ve tried swapping memory sticks and running low-level diagnostic and intensive burn-in tests, but at the end of the day there’s only so much you can do.     I must admit to feeling a tad forlorn. This machine has been a true and faithful companion for several years now. It was actually a refurbished unit I purchased off eBay for around $350. The graphics card was a beast that could drive two high-resolution monitors. I soon discovered that a new card of the same type would have cost me around $450 (eek!), but then I tracked down a refurbished version on eBay for something like $30. Since that time, I’ve been working the poor little scamp into the ground, pounding away on my keyboard, orchestrating things with my mouse, creating blogs, editing images, and doing suchlike from dawn till dusk, day-in and day-out. I know how frazzled I feel, so I’m not surprised that my tower computer eventually gave up the ghost and shrugged off this mortal coil.   The thing is that I can’t survive without my big-boy computer. I can struggle along on my notepads – as I must do when I’m travelling -- but I can generate only a fraction of the throughput I manage on my primary setup. If you couple this with the fact that I am a man of little patience, who is not prepared to wait several days to obtain a new machine, you can see we have a problem.   Of course one can find computers at places like Best-Buy and Walmart, but these are pretty much generic boxes targeted at the masses. These machines may be OK for home use, but I haven’t had much luck over the years using them in a grueling professional environment.   Fortunately, I have a chum called Daniel Imsand who works at a local company called GigaParts . This is an interesting organization with two faces to it. On one hand it is the largest independent ham radio distributor in the USA (and possibly in the world). On the other it builds and sells kick-ass PCs. The GigaParts Zero Systems brand is divided into three categories: Zero Home PCs, Zero Gaming PCs, and Zero Workstations.   Daniel is the product manager for all of GigaParts' Zero Systems. He is tasked with creating custom configurations with great pricing boasting the most reliable and stable components. As Daniel told me, GigaParts includes parts and labor warranty -- three years for both on the machine I ended up purchasing from them. But, given a choice, it prefers not to have to do any warranty work, so the company designs and builds its machines in such a way that they keep going, and going, and …   A lot of GigaParts' computer business involves creating custom value-added systems that it builds to order. (Apparently it does a roaring trade in professional-grade flight simulators.) But it also offers prebuilt, off-the-shelf systems sufficient to make even a grizzled old engineer like me squeal with delight. (It was not a pretty sound.)   I called Daniel on the phone. Based on his recommendation, I settled on a Zero Pro Z7 Plus machine. This little beauty boasts a quad-core Intel Core i7-4790 processor running at 3.6 GHz (be still, my beating heart). This is augmented by 16GB of DDR3-1600 RAM, an enterprise-grade Intel Pro 2500 Series 240GB SSD (solid state drive), an nVidia Quadro K620 Workstation GPU, SuperSpeed USB 3.0, and more bells and whistles than you could swing a stick at.   One thing I really like is that the company offers this machine with Microsoft Windows 7 Professional 64-Bit. (I have little regard for Windows 8 on my office machines.) As soon as I got off the phone with Daniel, I leapt into my truck and raced over to the GigaParts building. By the time I arrived, about 20 minutes later, my new machine, along with a bunch of HDMI cables and appropriate connectors, was sitting on the counter waiting for me. After undergoing a few formalities, like paying for the little scamp (thank goodness for credit cards, is all I can say), I zipped back to my office and commenced connecting everything together.     To be honest, after spending the past several months trying to keep my old machine gasping along, I've grown a little tired of crawling around under my desk, replacing parts and messing around with cables. Thus, I decided to locate this new machine on the top of my desk behind the monitors, as shown in the picture above.   I then spent the rest of the day downloading and/or reloading my various applications, like Microsoft Office, Microsoft Visio, Paint.net, and so forth. I also downloaded Mozilla Firefox, which is my preferred Web browser, and I made sure that Google.com is the default search engine that appears on the screen when I launch that browser.   Then the next day -- a brand spanking new day. Once again I'm wearing my happy face and all is now well in the Land of Max, where the colors are brighter, the butterflies are bigger, the birds sing sweeter, and the beer is plentiful and cold. I just powered up "the beast." OMG, this machine is so fast ! The password box appears on the center screen only a second or so after you've pressed the soft power button. As soon as you enter the password all three screens immediately spring to life. When I launch an application like Word or Excel, it appears on my screen in a flash. It's so fast, in fact, that I get the impression the program has launched before I've finished double-clicking its icon on my desktop.   Having said all this, I have run into one slight problem. I think this came about when I downloaded a new copy of the free PDFCreator utility that I've been using for years, but I can’t say for sure. All I know is that now, when I launch Firefox, I'm presented with the Google search engine on the initial tab, which is what I want. But if I subsequently click the '+' icon to open up a new tab, that tab appears with the loathsome Bing search engine flaunting itself in all its horrible glory. I've tried playing with the "options" settings, but for the life of me I can’t work out how to stop this from happening.   Are you aware of any problems associated with downloading PDFCreator, and do you have any ideas as to how I can banish the despicable Bing search engine back to the nether regions from whence it came?
  • 热度 5
    2013-11-18 21:52
    1447 次阅读|
    0 个评论
    In this story, I will tell how I solved an intermittent RAM semiconductor memory problem using music. In 1978, I met three brothers who owned a large machine shop in Ottawa, and they agreed to test a computer-controlled milling machine for me. I designed and built a self-programmable, point-to-point, numerical control (NC) system for a two axis Excello 602 milling machine. The system used closed loop stepper motors in the X and Y axis to keep the servos honest, and the Z axis used an air operated quill, which had a rotating cutter attached to it. Memory was programmed at the machine tool using a small keyboard, which was unheard of at that time. A magnetic digital cassette unit stored the programs for future production runs. No paper tape was used. The plan was for all four of us to get into business to manufacture these systems. I had started this project on my own in my flat, and now moved to the machine shop to finish it. I had no staff and very limited funds. The it. All went well until we started testing the machine. It would work smoothly for a while, but then it would intermittently mill faulty aluminium parts, or suddenly miss a step, or cut an incorrect hole in the work piece. Sometimes it would even threaten to cut into the milling machine table! This appeared to be a memory problem, but I didn't know how to fix it. Yet, I had to solve this problem or the project would fail. I only had a 10MHz dual trace oscilloscope and a 4 digit DVM. So, what was the problem? Was it system timing, or bad chips? The memory board used 32 static RAM ICs, so locating the faulty one was going to be challenging. A 1024 x 32bit word static RAM memory (2102s) was the heart of the system. This was new technology at the time. The NC system used BCD (binary coded decimal) numbers programmed into the memory that advanced through it to fabricate the parts. If the memory information was faulty, the machine would make scrap pieces. My partners running the machine shop wanted results, and I did not have a lot of time to convince them that this system was a viable product. The solution came from my childhood musical training, which gave me an idea—play music through the system! The NC system had a programmable audio tone generator, which was used to alert the operator to change parts when fabrication was completed, so it could be programmed to play a song. Musical patterns are similar to machine instructions. All the system timing stayed the same so it was a realistic test. RAM chips were quite expensive so there were few spares. I picked the song "Raindrops Keep Falling on My Head" because it was long enough to fill the memory and the tone generator could handle the range. It was a popular song at the time, so the operators would know if it sounded okay, or not. When humans listen to music they can detect a small error right away. When I played the song, I found the problem quite soon because the machine played wrong notes where the memory was faulty. I just had to go to that area of the music in the program RAM to find it. This saved a huge amount of time and expense trying to find the faulty memory. Later, when the NC system was introduced to the production floor, the machinists were fascinated by the music. Music became part of the diagnostic routines every day to test the memory. Everyone was happy with the machine and my partners gained a lot of machining contracts. Machine shop customers were thrilled by the musical milling machine. The NC machine worked flawlessly for a very long time after this, and to this day, I remember the feelings of excitement and pride the building of this machine and my creative solution gave me. John Barnhardt/VE3ZOV is a seasoned electronics designer (14 years)—avionics (Computing Devices), test engineering, and Lottario terminal manager (Consolidated Computer) and NC control designer (Campagna Brothers Machine Shop). He went to sales management for 18 years (Motorola Semiconductor, Ontario Centre for Microelectronics, CTS Corp.) and Component Engineering (JDS Uniphase). He submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  
  • 热度 2
    2013-8-28 17:20
    279 次阅读|
    0 个评论
      我司是韩国EMLSI和美国Everspin半导体中国区指定代理.  公司主要产品有: 1,Low power SRAM (低功耗静态随机存储器)1Mbit~8Mbit.  2,SPI SRAM(串行静态随机存储器)64Kbit~512Kbit.  3,PSRAM (虚拟静态随机存储器)4Mbit~64Mbit.  4,Cellular RAM(伪静态随机存储器)4Mbit~64Mbit.  5,Die(祼片)1Mbit~64Mbit.  6.NvSRAM,F-RAM,MRAM(非易失性存储器)256Kbit~1Gbit  7.MCP 512Mbit+256Mbit,1Gbit+512Mbit,64Mbit+32Mbit,128Mbit+64Mbit,32Mbit+16Mbit  8.Mobile SDRAM/DDR(低功耗SDRAM/DDR)128Mbit~512Mbit     Pseudo SRAM,UtRAM,Cellular RAM 型号及参数如下: Density     Voltage      Part Name                       Package ----------------------------------------------------------------------- 64Mbit       1.8V         EMC645SP16AKY-70LF        54BGA  64Mbit       1.8V         EMC643SP16AJY-70LF         54BGA  64Mbit       1.8V         EMC643SP16AKY-70LF        54BGA  64Mbit       1.8V         EMC646SP16AJY-70LF         54BGA  64Mbit       1.8V         EMC646SP16AKY-70LF        54BGA  64Mbit       1.8V         EM7644SP16LP-70LFx         48BGA  64Mbit       1.8V         EM7644SP16MP-70LFx        48BGA  64Mbit       1.8V         EM7644SP16NP-70LFx        48BGA  64Mbit       1.8V         EM7644SP16PP-70LFx        48BGA  64Mbit       1.8V         EM7644SP16RP-70LFx        48BGA  64Mbit       1.8V         EM7644SP16SP-70LFx        48BGA  64Mbit       3.0V         EM7644SU16ALP-70LFx      48BGA  64Mbit       3.0V         EM7644SU16AMP-70LFx     48BGA  64Mbit       3.0V         EM7644SU16ANP-70LFx     48BGA  64Mbit       3.0V         EM7644SU16APP-70LFx     48BGA  64Mbit       3.0V         EM7644SU16ARP-70LFx     48BGA  64Mbit       3.0V         EM7644SU16ASP-70LFx     48BGA  -----------------------------------------------------------------------     32Mbit       1.8V         EMC325SP16AKY-70LF       54BGA  32Mbit       1.8V         EMC323SP16AJY-70LF        54BGA  32Mbit       1.8V         EMC323SP16AKY-70LF       54BGA  32Mbit       1.8V         EMC326SP16AJY-70LF        54BGA  32Mbit       1.8V         EMC326SP16AKY-70LF       54BGA  32Mbit       1.8V         EM7324SP16LP-70LFx        48BGA  32Mbit       1.8V         EM7324SP16MP-70LFx       48BGA  32Mbit       1.8V         EM7324SP16NP-70LFx       48BGA  32Mbit       1.8V         EM7324SP16PP-70LFx       48BGA  32Mbit       1.8V         EM7324SP16RP-70LFx       48BGA  32Mbit       1.8V         EM7324SP16SP-70LFx       48BGA  32Mbit       3.0V         EM7324SU16LP-70LFx       48BGA  32Mbit       3.0V         EM7324SU16MP-70LFx      48BGA  32Mbit       3.0V         EM7324SU16NP-70LFx      48BGA  32Mbit       3.0V         EM7324SU16PP-70LFx      48BGA  32Mbit       3.0V         EM7324SU16RP-70LFx      48BGA  32Mbit       3.0V         EM7324SU16SP-70LFx      48BGA  -----------------------------------------------------------------------     16Mbit      1.8V         EMC165SP16KY-70LF          54BGA  16Mbit      1.8V         EMC163SP16JY-70LF           54BGA  16Mbit      1.8V         EMC163SP16KY-70LF          54BGA  16Mbit      1.8V         EMC166SP16JY-70LF           54BGA      16Mbit      1.8V         EMC166SP16KY-70LF          54BGA  16Mbit      1.8V         EM7164SP16LP-70LFx        48BGA  16Mbit      1.8V         EM7164SP16MP-70LFx       48BGA  16Mbit      1.8V         EM7164SP16NP-70LFx       48BGA  16Mbit      1.8V         EM7164SP16PP-70LFx       48BGA  16Mbit      1.8V         EM7164SP16RP-70LFx        48BGA  16Mbit     1.8V          EM7164SP16SP-70LFx        48BGA  16Mbit     3.0V          EM7164SU16BLP-70LFx      48BGA  16Mbit     3.0V          EM7164SU16BMP-70LFx     48BGA  16Mbit     3.0V          EM7164SU16BNP-70LFx     48BGA  16Mbit     3.0V          EM7164SU16BPP-70LFx     48BGA  16Mbit     3.0V          EM7164SU16BRP-70LFx     48BGA  16Mbit     3.0V          EM7164SU16BSP-70LFx     48BGA     Low power SRAM,Serial SRAM型号及参数如下:   Desity         Part Name         Org.             Package            Voltage ---------------------------------------------------------------------------- 8Mbit          EM680FV8BU      1Mx8bit          44TSOP2        2.7~3.6V  8Mbit          EM681FV8BU      1Mx8bit          44TSOP2        2.7~3.6V  8Mbit          EM680FV8B        1Mx8bit          48BGA            2.7~3.6V  8Mbit          EM681FV8B        1Mx8bit          48BGA            2.7~3.6V  8Mbit          EM681FV16BU    512Kx16bit    44TSOP2         2.7~3.6V  8Mbit          EM680FV16B       512Kx16bit    48BGA            2.7~3.6V  8Mbit          EM681FV16B       512Kx16bit    48BGA            2.7~3.6V  --------------------------------------------------------------------------     4Mbit          EM641FT8S         512Kx8bit      32 STSOP1     5.0V  4Mbit          EM641FV8FS       512Kx8bit      32 STSOP1     2.7~3.6V  4Mbit          EM643FV16FU     256Kx16bit    44 TSOP2       2.7~3.6V  4Mbit          EM644FV16FU     256Kx16bit    44 TSOP2       2.7~3.6V  4Mbit          EM645FV16FU     256Kx16bit    44 TSOP2       2.7~3.6V  4Mbit          EM646FV16FU     256Kx16bit    44 TSOP2       2.7~3.6V  4Mbit          EM643FV16F       256Kx16bit    48BGA            2.7~3.6V  4Mbit          EM644FV16F       256Kx16bit    48BGA            2.7~3.6V  4Mbit          EM645FV16F       256Kx16bit    48BGA            2.7~3.6V  4Mbit          EM646FV16F       256Kx16bit    48BGA            2.7~3.6V  4Mbit          EM640FV16F       256Kx16bit    48BGA            2.7~3.6V  4Mbit          EM641FV16F       256Kx16bit    48BGA            2.7~3.6V  ---------------------------------------------------------------------------  2Mbit         EM620FV8BS      256Kx8bit       32 STSOP1      2.7~3.6V  2Mbit         EM621FV8BS      256Kx8bit       48BGA             2.7~3.6V  2Mbit         EM620FV16B      128Kx16bit     32 STSOP1      2.7~3.6V  2Mbit         EM621FV16B      128Kx16bit     48BGA             2.7~3.6V ---------------------------------------------------------------------------    1Mbit         EM610FV8S       128Kx8bit        32 STSOP1     2.7~3.6V  1Mbit         EM610FV16U     64Kx16bit        44 TSOP2       2.7~3.6V  1Mbit         EM611FV16U     64Kx16bit        44 TSOP2       2.7~3.6V  1Mbit         EM610FV8T       128Kx8bit        32 STSOP1     2.7~3.6V                     我司是美国Everspin半导体中国区指定代理. Everspin MRAM是一种具有革命性的存储器,其原理是利用电子自旋的磁性结构,  来提供不会产生损耗的非挥发特性。Everspin MRAM可在集成了硅电路的磁性材  料中存储信息,以在单一、可无限使用的组件中提供SRAM的速度以及闪存的非挥发特性。     主要代理MRAM(非易失性存储器),可完全替代SRAM,NvSRAM,F-RAM,EEPROM,BBSRAM,FLASH容量有:   串口:256Kbit,1Mbit,4Mbit   型号                容量     数据结构    总线速度     工作电压     工作温度     封装 MR25H256     256Kb     32K*8       40MHz       2.7V~3.6V     C,M         8-DFN  MR25H10       1Mb       128K*8      40MHz       2.7V~3.6V     C,M         8-DFN  MR25H40       4Mb       512K*8      40MHz       2.7V~3.6V     C,M         8-DFN,8-DIP     并口(*8bit):256Kbit,1Mbit,4Mbit 型号                 容量     数据结构    总线速度     工作电压                工作温度     封装 MR256A08B       256Kb     32K*8       35ns         2.7V~3.6V               C,M         44TSOP,48-BGA  MR0A08B           1Mb       128K*8      35ns         2.7V~3.6V               C,M         44TSOP,48-BGA  MR0D08B           1Mb       128K*8      45ns         2.7V~3.6V,I/O 1.8V      Blank       48-BGA  MR2A08A           4Mb       512K*8      35ns         2.7V~3.6V               C,M         44TSOP,48-BGA  MR4A08B           16Mb      2Mb*8       35ns         2.7V~3.6V               C,M         44TSOP,48-BGA     并口(*16bit):1Mbit,4Mbit,16Mbit 型号                容量     数据结构    总线速度     工作电压                工作温度     封装 MR0A16A         1Mb       64K*16      35ns         2.7V~3.6V               C,M         44TSOP,48-BGA  MR2A16A         4Mb       256K*16      35ns         2.7V~3.6V               C,M         44TSOP,48-BGA  MR4A16B         16Mb      1Mb*16       35ns         2.7V~3.6V               C,M         54TSOP,48-BGA     我司产品可完全替代FRAM(铁电存储器),NV-SRAM,MRAM,如有需要请随时和我们联系. 如以下型号:   CY14B064I       CY14ME064       CY14B101KA      CY14B108N  CY14B064P       CY14B101Q       CY14B101LA      CY14B256KA  CY14B101Q       CY14C101J       CY14B101MA      CY14E256LA  CY14B101I       CY14B256P       CY14B101NA      CY14V101LA  CY14C101I       CY14B256Q       CY14B104K              CY14V101NA  CY14B101P       CY14B512I       CY14B104LA      CY14V104LA  CY14E256Q       CY14B512P       CY14B104M              CY14V104NA  CY14MB064       CY14B512Q       CY14B104NA      STK11C88  CY14MB256       CY14B101Q       CY14B108K              STK14C88  CY14B108M       STK16C88       CY14B108L              STK15C88     FM23MLD16        FM25H20           FM1808         FM18W08  FM22L16                 FM25V10           FM18L08         FM1808B  FM22LD16         FM25V05           FM24C512         FM28V010  FM21L16                 FM25V02           FM24L256         FM25L256B  FM21LD16         FM25W256   FM24C256         FM25256B  FM28V100         FM25V01           FM24V05         FM24V10  FM28V020         FM25L512   FM24W256         FM24V01  FM24V02       英尚国际有限公司(EVERSPINEMLSI中国区代理(主营:SRAM,PSRAM,UtRAM,MCP,Mobile SDRAM,MRAM,Nv-RAM,FRAM) -Http://www.sramsun.com.   如有需要请随时和我们联系. 我们原厂供货,价格交期较有优势. 谢谢! ----------------------------- Sandy(苏女士) Ramsun International Limited. 英尚国际有限公司 M/P:86-137 9533 2690  e_mail:sandy@sramsun.com  QQ:1537376816 tel:021-6678 7052
  • 热度 9
    2011-5-30 14:26
    2607 次阅读|
    6 个评论
    说起存储器IC的分类,大家马上想起可以分为RAM和ROM两大类。   RAM是Random Access Memory的缩写,翻译过来就是随机存取存储器,随机存取可以理解为能够高速读写。常见的RAM又可以分成SRAM(Static RAM:静态RAM)和DRAM(dynamic RAM:动态RAM)。   ROM是Read Only Memory的缩写,翻译过来就是只读存储器。常见的ROM又可分为掩膜ROM(有时直接称为ROM)、PROM(Programmable ROM:可编程ROM,特指一次编程的ROM)、EPROM(Erasable Programmable ROM:可擦除可编程的ROM,擦除时用紫外线)、EEPOM(Electrically Erasable Programmable ROM:电可擦除可编程ROM)。   以上是大家在各种教材上看到的存储器的分类。   问题是,ROM明明叫只读存储器,也就是不可写的存储器,现实是除了掩膜ROM是不可写的外,PROM、EPROM、EEPOM事实上都是可写的。它们的名称中还带有“ROM”是名不副实的叫法。掩膜ROM、PROM、EPROM、EEPOM这几种存储器的共同特点其实是掉电后,所存储的数据不会消失,所以可以归类为非易失性存储器(即Non-Volatile Memory)。   SRAM、DRAM的共同特点是掉电后数据会丢失,所以也可称为易失性存储器(Volatile memory)。   于是,存储器从大类来分,可以分 为易失性存储器和非易失性存储器。   后来出现的Flash Memory(快闪存储,简称闪存),掉电后数据也不容易丢失,所以也属于非易失性存储器。Flash Memory的名称中已经不带ROM字样了,但是传统的分类方法中,还是把Flash Memory归类为ROM类,事实上此时是因为这些存储器都是非易失的。   把存储器分为易失性存储器和非易失性存储器就万事大吉了么?   令人纠结的是,有一种新的存储器,它既是非易失的,同时又是能够高速随时读写数据的,也就是说能够随机存取的。这种存储器就是FRAM(Ferroelectric Random Access Memory:铁电随机存取存储器,简称铁电存储器)。把FRAM归类为非易失性存储器是可以,但是FRAM的高速读写性质又与SRAM、DRAM更为接近,它也是一种RAM。   于是,存储器的分类令人纠结。传统的分为RAM与ROM的方式本来就不科学。如果按分成RAM与非易失性存储器这两大类,也不科学,因为这个分类本身就不是按同一个标准分,导致FRAM即属于RAM,又属于非易失性存储器。如果只分成易失性存储器和非易失性存储器,又导致FRAM与SRAM、DRAM分家,大家都有RAM嘛,凭什么分开是吧。   我的建议是,存储器分成随机存取存储器和非随机存取存储器两大类比较合适。   于是,存储器的分类如下(按存取速度分类):   随机存取存储器:SRAM、DRAM、FRAM; 非随机存取存储器:掩膜ROM、PROM、EPROM、EEPOM、Flash Memory。 差强人意的分类为(按易失性分类):   易失性存储器:SRAM、DRAM; 非易失性存储器:掩膜ROM、PROM、EPROM、EEPOM、Flash Memory、FRAM。
相关资源
广告