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3ASC25H208工業(yè)控制卡
地址一致性或地址一致性是指XVME-660和VMEbus，其中兩種架構的地址均相同字節(jié)換言之，XVME-660和VMEbus存儲器圖像看起來相同。面向字節(jié)的數據（如字符串或視頻圖像）需要地址一致性數據考慮使用以下方法將字符串文本傳輸到VMEbus內存的示例：圖4-4中的32位傳輸。注意每個地址的數據字節(jié)是相同的。為此，數據字節(jié)需要當它們從PCI總線傳送到VMEbus時進行交換。保持地址一致性，通過設置閃存的設置位6和7啟用字節(jié)交換緩沖區(qū)尋呼和字節(jié)交換寄存器（寄存器234h）均為1（見第17頁）。即硬件字節(jié)交換已啟用，因此tundra數據不變被中和。有三個Xycom自動化軟盤驅動器和硬盤驅動器擴展模塊：
XVME-977（硬盤驅動器和軟盤驅動器）、XVME-979（CD-ROM、硬盤驅動器、軟盤驅動器連接器）和XVME-973（硬盤和軟盤驅動器連接器）。有單獨的XVME-977和XVME-979手冊；本章介紹了XVME-973。
XVME-973/1驅動器適配器模塊用于連接外部硬盤驅動器和XVME-660模塊的軟盤驅動器。它有一個單邊緣連接器，標記為P2連接到VME機箱后部的P2背板連接器。
如何將XVME-973/1連接到VME機箱底板P2連接器。
XVME-973/1模塊上有四個接頭，用于連接最多兩個IDE硬盤驅動器和一個3.5英寸軟盤驅動器。本章介紹了所有連接器的引腳。P3連接器用于單個3.5“軟盤驅動器，P5連接器用于單個許多筆記本電腦中都有3.5英寸軟盤驅動器。這兩種連接器被路由到P2連接器上的相同信號線，因此一次可以使用一條。同樣，P1連接器最多連接兩個標準3.5英寸硬盤驅動器，P4連接器最多連接2個2.5英寸的硬盤驅動器。這兩個接頭也使用相同的P2連接器信號線，因此一次只能使用一條。XVME-973/1隨附P1和P3接頭的電纜。皮諾
本章可作為P2和P4連接器電纜的參考。IDE控制器支持增強的PIO模式，這減少了向硬盤傳輸16位數據的周期時間。與您的驅動器手冊，查看您使用的驅動器是否支持這些模式。這個PIO模式越高，循環(huán)時間越短。作為IDE電纜長度循環(huán)時間的減少會導致不穩(wěn)定的操作。因此，保持IDE電纜盡可能短符合您的最佳利益。
可以在BIOS設置中選擇PIO模式（參見第36頁）。如果驅動器：支持自動ID命令。如果遇到問題，請更改將模式轉換為標準模式。
Address Consistency
Address consistency, or address coherency, refers to communications between the
XVME-660 and the VMEbus in which both architectures' addresses are the same for each
byte. In other words, the XVME-660 and the VMEbus memory images appear the same.
Address consistency is desirable for byte-oriented data such as strings or video image
data. Consider the example of transferring the string Text to the VMEbus memory using
a 32-bit transfer in Figure 4-4. Notice that the data byte at each address is identical. To achieve this, the data bytes need
to be swapped as they are passed from the PCI bus to the VMEbus. To maintain address
consistency, enable the byte-swapping buffers by setting setting bits 6 and 7 of the Flash
Paging and Byte Swap register (register 234h) both to 1 (see p. 17). That is, hardware
byte swapping is enabled, so tundra data invariation is neutralized. There are three Xycom Automation floppy drive and hard drive expansion modules: the
XVME-977 (hard drive and floppy drive), the XVME-979 (CD-ROM, hard drive, floppy
drive connector), and the XVME-973 (hard and floppy drive connectors). There are separate XVME-977 and XVME-979 manuals; the XVME-973 is described in this chapter.
The XVME-973/1 Drive Adapter Module is used to connect an external hard drive and a
floppy drive to your XVME-660 module. It has a single edge connector, labeled P2 that
connects to the P2 backplane connector on the rear of the VME chassis. Figure 5-1 illustrates how to connect the XVME-973/1 to the VME chassis backplane P2 connector. The XVME-973/1 module has four connectors on it for the connection of up to two IDE
hard drives and one 3.5" floppy drive. Pinouts for all of the connectors are in this chapter.
The P3 connector is for a single 3.5" floppy drive and the P5 connector is for a single
3.5" floppy drive of the type found in many laptop computers. Both of these connectors
are routed to the same signal lines on the P2 connector, so one may be used at a time.
Similarly, the P1 connector connects up to two standard 3.5" hard drives and the P4 connector connects up to two 2.5" hard drives. Both of these connectors also use the same P2
connector signal lines, so only one may be used at a time.
The XVME-973/1 is shipped with cables for the P1 and the P3 connectors. The pinouts in
this chapter may be used as references to make cables for the P2 and P4 connectors. The IDE controller supports enhanced PIO modes, which reduce the cycle times for 16-bit data transfers to the hard drive. Check with your
drive manual to see if the drive you are using supports these modes. The
higher the PIO mode, the shorter the cycle time. As the IDE cable length
increases, this reduced cycle time can lead to erratic operation. As a result, it is in your best interest to keep the IDE cable as short as possible.
The PIO modes can be selected in the BIOS setup (see p. 36). The Autoconfiguration will attempt to classify the connected drive if the drive
supports the auto ID command. If you experience problems, change the
Transfer Mode to Standard.
