外文翻譯---串行存儲(chǔ)器(文件)
【正文】 SPI ports, allow you to adjust the clock speed for the SPI port with a clock scalar. Thus, if you are connecting a 25LC640, for example, to a 16mhz 68HC12, you will need to select an SPI presale that slows the SPI bus down to 2mhz. This is a mon oversight, and a good source of bugs!Cycle lifeSerial EPROM’s are typically rated to endure 1 million write operations per byte. That’s pretty decent. However, you still need to be careful here that you are not constantly writing data to the part. EEPROM is not a substitute for general purpose RAM. If you write to these parts in a tight loop, it would only take an hour or so to exceed the 1million write operations. Your software needs to be written to take that into account. SoftwareAs you can see, wiring up an SPI based EEPROM to the SPI port is relatively simple. Nothing es for free, however, and you will find the software mands needed to work with the SPI memory is a little more plex than just doing memory writes. The basic operation of the SPI based EPROM’s is to lower the CS line, send a mand, such as WRITE, followed by an address and the data, then raise the CS line. In a WRITE operation, raising the CS line causes the EEPROM to actually store the data. That is an important point you don39。t what you wanted to do!I have written a set of routines in Image craft 39。Void sermem_Read (unsigned char *puffin cuff)。Void sermem_Write (unsigned char *puffin cuff)。You can find the full source code in and , which are fairly well mented and pretty easy to follow. This code is written for the 68HC12 series of chips, but is really trivial to port to the 68HC11 (an excursive left to the reader!). Another file is called , which is a test program that uses the routines.The Status RegisterAn important part of the serial EEPROM is the status register. I thought it important to point it out that you need to use this register. This register not only holds some configuration data that you will need to write to, it also contains an important bit called the WIP bit standing for Write In Progress. Serial EEPROM requires a burn time while it is saving data to the array. This can take up to 5 milliseconds, though it might be less. Rather than relying on a timer on your micro controller, you can check the status of this WIP flag to know when the part has finished writing the page and is ready for new data. Void sermem_StopWrite (void){ // // Raise the CS line. That makes the memory part start its write cycle // Then wait for the WIP bit to be cleared // Do { spi_deselect ()。 0x01)。SummarySerial EEPROM provide a great way to store nonvolatile data on a small micro controller project. They require few I/O lines, relatively fast read/write operations, and most operate from a single 5volt power supply. The software routines to drive these parts are not very plex. Next time you need to store some nonvolatile data, such as configuration information or navigation maps, consider serial EEPROM.串行存儲(chǔ)器概述我們中的許多人喜歡使用小型的獨(dú)立芯片微控制器。這里能提供幫助！有幾種形式的存儲(chǔ)器不需要標(biāo)準(zhǔn)地址總線和數(shù)據(jù)總線配線方式。也有1線，2線和3線式串行電擦除可編程存儲(chǔ)器器件，它們以相似的方式工作，但是具有不同的接口邏輯。例如，檢驗(yàn)以下兩個(gè)封裝。其中有1條輸入線，1條輸出線，1條控制線，還需要1條時(shí)鐘線。由于串行電擦除可編程存儲(chǔ)器每次訪問一個(gè)bit，這要付出速度上的代價(jià)。所以，對(duì)于小數(shù)量的軟件開銷和僅僅4個(gè)I/O引腳，你可以為自己存儲(chǔ)一些基本數(shù)據(jù)。所有這些器件在電氣上都是兼容的。顯然，串行電擦除可編程存儲(chǔ)器可以從幾個(gè)不同的廠商那里得到?；A(chǔ)部分這些器件之一具有8個(gè)引腳。CS線不僅使能器件，而且作為操作結(jié)束的標(biāo)志。從串行電擦除可編程存儲(chǔ)器輸出的數(shù)據(jù)在此線上隨時(shí)鐘輸出。其它選擇時(shí)，WP被置為高電平。6SCK串行時(shí)鐘。通過將此線拉低，器件將忽略SCK線，這實(shí)際上引起器件掛起它的當(dāng)前狀態(tài)。通常接5V。其他部分也是有趣的，但是在這篇文章里我將忽略它們。接下來示意的圖片展示了連接到板子SPI端口的25xxx串行EEPROM。注意，我已經(jīng)選擇將WP和HOLD線接為高電平。以下表格是一個(gè)簡單的總結(jié)。一套完整的指令及格式可以在你的特殊器件的數(shù)據(jù)手冊上得到。幸運(yùn)的是，多數(shù)SPI的執(zhí)行，例如68HC11和68HC12的SPI端口，允許你根據(jù)時(shí)鐘標(biāo)量來調(diào)整SPI端口的時(shí)鐘速度。然而，在這里你仍然需要注意，你并不是不斷地給器件寫數(shù)據(jù)。軟件正如你所見到的，基于EEPROM的SPI配線到SPI端口相對(duì)簡單。這是你不想丟掉（數(shù)據(jù)）的關(guān)鍵！串行EEPROM允許你以頁模式進(jìn)行寫操作，那意味著你每次能發(fā)送1頁數(shù)據(jù)。思路是每次地址跨越一頁，你需要升高CS線以便芯片能將一頁數(shù)據(jù)寫入存儲(chǔ)器。我把如下資源的鏈接包括在內(nèi)了。讀/寫操作工作于相同的基本方式。為了使用容易，我還定義了一個(gè)稱為sermem_ReadBlock()的函數(shù)，它能一次執(zhí)行全
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