基于ARM920T微處理器的IDE硬盤接口設(shè)計(jì)與實(shí)現(xiàn)

1、    基于ARM920T微處理器的IDE硬盤接口設(shè)計(jì)與實(shí)現(xiàn)        何明聰 胡繼承 孫世磊 時(shí)間:2010年01月28日     字 體: 大 中 小        關(guān)鍵詞:<"cblue" " target='_blank'>ARM<"cblue" " t

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3、#160;    1 引言    20世紀(jì)90年代后期，嵌入式系統(tǒng)在工業(yè)控制、遠(yuǎn)程監(jiān)控和數(shù)據(jù)采集等領(lǐng)域的應(yīng)用日趨廣泛，人們對嵌入式系統(tǒng)的存儲(chǔ)容量也提出了較高的要求。因此研制適用于嵌入式系統(tǒng)的大容量、高速率、高可靠性的數(shù)據(jù)存儲(chǔ)系統(tǒng)變得日益重要。本文針對一款基于<"cblue" " " title="ARM">ARM" title="ARM">ARM" title="ARM">ARM&q

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38、t;ARM">ARM" title="ARM">ARM920T芯片的開發(fā)板，根據(jù)ATA硬盤<"cblue" " title="接口">接口規(guī)范，設(shè)計(jì)了IDE硬盤接口電路，實(shí)現(xiàn)了對IDE硬盤的讀寫，可以在Linux系統(tǒng)中對其上的文件系統(tǒng)自由訪問，達(dá)到了高速率和高可靠性的要求。2 <"cblue" " title="ARM920T">ARM920T與S3C2410介紹    ARM 包

39、括一系列微處理芯片技術(shù)。ARM920T是ARM系列微處理器的一種，它采用5階段管道化ARM9TDMI內(nèi)核，同時(shí)配備了Thumb擴(kuò)展、EmbeddedICE調(diào)試技術(shù)和Harvard總線。在生產(chǎn)工藝相同的情況下，性能可達(dá)ARM7TDMI芯片的兩倍之多。ARM920T系列主要應(yīng)用于機(jī)頂盒產(chǎn)品、掌上電腦、筆記本電腦和打印機(jī)。    S3C2410處理器是Samsung 公司基于ARM公司的ARM920T處理器核，采用0.18umSU造工藝的32位微控制器。該處理器擁有獨(dú)立的16KB指令Cache和16KB數(shù)據(jù)Cache、MMU、支持TFT的LCD控制器、NAND閃存控制器

40、、3路UART、4路DMA、4路帶PWM的Timer、I/O口、RTC、8路10位ADC、TouchScreen接口、IIC-BuS接口、IIS-BuS接口、2個(gè)USB主機(jī)、1個(gè)USB設(shè)備、SD主機(jī)和MMC接口和2路SPI。S3C2410處理器最高可運(yùn)行在268MHz。3 IDE接口及其規(guī)范    IDE(Integrated Drive Electronics)是從IBM PC/AT上使用的ATA接口發(fā)展而來的。IDE/ATA磁盤驅(qū)動(dòng)器與早期的ATA驅(qū)動(dòng)器相比，增加了任務(wù)文件寄存器，包括數(shù)據(jù)寄存器、狀態(tài)寄存器以及反映地址的驅(qū)動(dòng)器號(hào)、磁頭號(hào)、道號(hào)和扇區(qū)號(hào)寄存器等。

41、ATA接口規(guī)范定義了信號(hào)電纜和電源線的電器特征、互聯(lián)信號(hào)的電器和邏輯特征，還定義了存儲(chǔ)設(shè)備中可操作的寄存器以及命令和協(xié)議。3.1 寄存器    規(guī)范定義了兩組寄存器：命令寄存器和控制寄存器。命令寄存器用來接收命令和傳送數(shù)據(jù)，控制寄存器用來控制磁盤操作。常用的寄存器包括數(shù)據(jù)寄存器、命令寄存器、驅(qū)動(dòng)器/磁頭寄存器、柱面號(hào)寄存器、扇區(qū)號(hào)寄存器、扇區(qū)數(shù)寄存器和狀態(tài)寄存器。3.2 數(shù)據(jù)傳輸方式    ATA接口規(guī)范定義了兩種數(shù)據(jù)傳輸方式：可編程I/O(PIO)方式和DMA方式。PIO傳送方式下，CPU對控制器的訪問都是通過PIO進(jìn)行的，包括從控

42、制器讀取狀態(tài)信息和錯(cuò)誤信息，以及向控制器發(fā)送命令和參數(shù)。在一次PIO數(shù)據(jù)傳輸過程中，CPU先選址，然后使讀/寫信號(hào)有效，CPU或控制器放數(shù)據(jù)到數(shù)據(jù)總線，控制器或CPU讀取數(shù)據(jù)，操作完成后，釋放總線，這樣一次數(shù)據(jù)傳輸完成。DMA方式，即直接內(nèi)存訪問，CPU把緩沖區(qū)的地址與需要讀寫的長度告訴外設(shè)，外設(shè)在準(zhǔn)備好后向CPU發(fā)出一個(gè)DMA請求，要求CPU暫停使用內(nèi)存，獲得同意后就直接在內(nèi)存和外設(shè)之間傳輸數(shù)據(jù)，完成后再把對內(nèi)存的訪問權(quán)歸還給CPU。4 硬件實(shí)現(xiàn)    如圖1所示，S3C2410與硬盤之間接口電路分為3個(gè)部分：片選信號(hào)、數(shù)據(jù)信號(hào)和控制信號(hào)。硬盤上寄存器分為兩組，

43、分別由IDE_CS0和IDE_CS1選中，DA0DA2則用于組內(nèi)寄存器尋址；數(shù)據(jù)線DD0DD15因存在輸入/輸出方向問題，故用nOE(讀信號(hào))接buffer(74LVTH162245)的DIR引腳來控制緩沖器方向；控制信號(hào)部分因該CPU與硬盤之間DMA時(shí)序不一致，故采用一塊EPM7032AETC44-7芯片用于調(diào)整其時(shí)序。PIO模式下，不需要DMARQ和nDMACK信號(hào)，DMA模式下，這兩個(gè)信號(hào)才起作用。5 軟件實(shí)現(xiàn)    硬盤驅(qū)動(dòng)程序?qū)崿F(xiàn)分為初始化、打開設(shè)備、設(shè)備I/O操作和釋放設(shè)備等幾部分。5.1 硬盤初始化    與X86不同，

44、在ARM 體系結(jié)構(gòu)中，對內(nèi)存和外設(shè)的訪問使用統(tǒng)一的指令，所以要對外設(shè)地址進(jìn)行內(nèi)存映射。也就是說，通過一張表將I/O地址映射到內(nèi)存空間中來，這部分工作是在系統(tǒng)初始化期間完成的。    在IDE子系統(tǒng)初始化期間，Linux系統(tǒng)一旦發(fā)現(xiàn)一個(gè)IDE控制器，就設(shè)置它的ide_hwif_t結(jié)構(gòu)來反映這個(gè)控制器和與之相連的磁盤；向Linux的VFS登記每一個(gè)控制器，并分別把它加到blk_dev和blkdevs向量表中；請求控制適當(dāng)?shù)腎RQ中斷(主IDE控制器是14，次IDE控制器是15)和I/O空間(主控制器0x1f0，次控制器0x170)：為每一個(gè)找到的IDE控制器在gend

45、isk列表中增加一個(gè)條目。    IDE硬盤的初始化工作由idedisk_init完成：    (1)在數(shù)組ide_hwifs中找出已登記得各IDE控制器控制的所有IDE硬盤(一個(gè)控制器最多控制兩個(gè)硬盤)，每個(gè)IDE硬盤對應(yīng)一個(gè)ide_drive_t結(jié)構(gòu)。    (2)對找到的每個(gè)IDE硬盤，調(diào)用函數(shù)ide_register_subdriver填寫各IDE硬盤結(jié)構(gòu)中的相關(guān)信息域，主要是填寫其驅(qū)動(dòng)程序結(jié)構(gòu)ide_driver_t。硬盤驅(qū)動(dòng)中的函數(shù)do_rw_disk通過向磁盤控制寄存器寫參數(shù)啟動(dòng)磁盤操作，完

46、成真正的數(shù)據(jù)讀寫。    (3)對找到的每個(gè)IDE硬盤，調(diào)用函數(shù)idedisk_setup進(jìn)一步設(shè)置其ide_drive_t結(jié)構(gòu)，包括設(shè)置該結(jié)構(gòu)的settings域、doorlocking域、cyl、head、sect域、id域等。5.2 打開設(shè)備    打開塊設(shè)備的操作與打開普通文件的操作基本相同。    (1)在當(dāng)前進(jìn)程的文件描述符表中為打開文件找一個(gè)空位，申請一塊內(nèi)存，用于建立新文件的打開文件對象，即結(jié)構(gòu)file。    (2)解析設(shè)備特殊文件名，獲得其VFSinode和dentry結(jié)構(gòu)，根據(jù)dentry結(jié)構(gòu)填寫file結(jié)構(gòu)，尤其是將file結(jié)構(gòu)的f_op域設(shè)為其VFSinode中的缺省文件操作。    (3)執(zhí)行該文件操作集中的open操作，即blkdev_open，它根據(jù)設(shè)備特殊文件的主次設(shè)備號(hào)從blkdevs向量表中取出已經(jīng)注冊的文件操作集(file_operations)fops，用該結(jié)構(gòu)代替file結(jié)構(gòu)中的f_op域。    (4)執(zhí)行中新文件操作集中的open操作，即bl帶頭kdev_open，它根據(jù)VFS