Vmebus Domain - Motorola MVME2700 Series Installation And Use Manual

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 Guide.
http://www.motorola.com/computer/literature
Programming Considerations
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