FI830F電源模塊,ABB使用范圍
PCI和以太網(wǎng)以太網(wǎng)也是面向字節(jié)流的；具有最低地址的字節(jié)在內(nèi)存中是第一個(gè)被傳輸?shù)?，無(wú)論端模式如何。由于Raven在小端和大端模式下都保持地址不變性，因此以太網(wǎng)數(shù)據(jù)不應(yīng)出現(xiàn)端問(wèn)題。Big-endian軟件仍然必須考慮字節(jié)交換效應(yīng)然而，當(dāng)訪問(wèn)PCI/Ethernet設(shè)備的寄存器時(shí)。Universe II ASIC的作用由于PCI總線是小端，
FI830F電源模塊而VMEbus是大端，因此Universe PCI/VME總線橋ASIC在這兩種總線中執(zhí)行字節(jié)交換維護(hù)的方向（從PCI到VMEbus和從VMEbus到PCI）地址不變性，與處理器的操作模式無(wú)關(guān)領(lǐng)域VMEbus域VMEbus本質(zhì)上是大端的。所有直接連接到的設(shè)備VMEbus必須在大端模式下運(yùn)行，而不管處理器域中的操作。在大端模式下，字節(jié)交換首先由Universe II執(zhí)行ASIC和Raven。結(jié)果對(duì)big endian是透明的軟件（理想效果）。
然而，在little endian模式下，軟件必須進(jìn)行字節(jié)交換Universe II ASIC的效應(yīng)和地址反向重排效應(yīng)考慮到烏鴉。有關(guān)endian注意事項(xiàng)的更多詳細(xì)信息，請(qǐng)參閱MVME2600/2700系列單板計(jì)算機(jī)程序員參考指南概述介紹了MVME2700系列單板計(jì)算機(jī)方框圖級(jí)別。圖3-1顯示了整個(gè)電路板的框圖建筑學(xué)一般說(shuō)明概述了MVME2700，然后詳細(xì)描述了電路。其他MVME2700區(qū)塊的詳細(xì)說(shuō)明，包括ASIC和外圍芯片中的可編程寄存器可在MVME2600/2700系列單板計(jì)算機(jī)程序員參考指南，見附錄D，相關(guān)文件。提到它更深入地描述了MVME2700的功能。
PCI and Ethernet
Ethernet is also byte-stream-oriented; the byte having the lowest address
in memory is the first one to be transferred regardless of the endian mode.
Since the Raven maintains address invariance in both little-endian and big-endian mode, no endian issues should arise for Ethernet data.
Big-endian software must still take the byte-swapping effect into account
when accessing the registers of the PCI/Ethernet device, however.
Role of the Universe II ASIC
Because the PCI bus is little-endian while the VMEbus is big-endian, the
Universe PCI/VME bus bridge ASIC performs byte swapping in both
directions (from PCI to VMEbus and from VMEbus to PCI) to maintain
address invariance, regardless of the mode of operation in the processor’s
domain.
VMEbus Domain
The VMEbus is inherently big-endian. All devices connected directly to
the VMEbus must operate in big-endian mode, regardless of the mode of
operation in the processor’s domain.
In big-endian mode, byte-swapping is performed first by the Universe II
ASIC and then by the Raven. The result is transparent to big-endian
software (a desirable effect).
In little-endian mode, however, software must take the byte-swapping
effect of the Universe II ASIC and the address reverse-rearranging effect
of the Raven into account.
For further details on endian considerations, refer to the MVME2600/2700
Series Single Board Computer Programmer’s Reference GuideOverview
This chapter describes the MVME2700 series single board computer on a
block diagram level. Figure 3-1 shows a block diagram of the overall board
architecture. The General Description provides an overview of the
MVME2700, followed by a detailed description of several blocks of
circuitry.
Detailed descriptions of other MVME2700 blocks, including
programmable registers in the ASICs and peripheral chips, can be found in
the MVME2600/2700 Series Single Board Computer Programmer’s
Reference Guide, listed in Appendix D, Related Documentation. Refer to
it for a functional description of the MVME2700 in greater depth.
