FI830F电源模块,ABB使用范围
PCI和以太网以太网也是面向字节流的；具有最低地址的字节在内存中是第一个被传输的，无论端模式如何。由于Raven在小端和大端模式下都保持地址不变性，因此以太网数据不应出现端问题。Big-endian软件仍然必须考虑字节交换效应然而，当访问PCI/Ethernet设备的寄存器时。Universe II ASIC的作用由于PCI总线是小端，
FI830F电源模块而VMEbus是大端，因此Universe PCI/VME总线桥ASIC在这两种总线中执行字节交换维护的方向（从PCI到VMEbus和从VMEbus到PCI）地址不变性，与处理器的操作模式无关领域VMEbus域VMEbus本质上是大端的。所有直接连接到的设备VMEbus必须在大端模式下运行，而不管处理器域中的操作。在大端模式下，字节交换首先由Universe II执行ASIC和Raven。结果对big endian是透明的软件（理想效果）。
然而，在little endian模式下，软件必须进行字节交换Universe II ASIC的效应和地址反向重排效应考虑到乌鸦。有关endian注意事项的更多详细信息，请参阅MVME2600/2700系列单板计算机程序员参考指南概述介绍了MVME2700系列单板计算机方框图级别。图3-1显示了整个电路板的框图建筑学一般说明概述了MVME2700，然后详细描述了电路。其他MVME2700区块的详细说明，包括ASIC和外围芯片中的可编程寄存器可在MVME2600/2700系列单板计算机程序员参考指南，见附录D，相关文件。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.
