Pci-Ethernet; Pci-Graphics; Universe's Involvement; Vmebus Domain - Motorola MVME2600 Series Reference Manual

PCI-Ethernet

Ethernet is byte stream oriented with the byte having the lowest address in
memory being the first one to be transferred regardless of the endian mode.
Since address invariance is maintained by the Raven in both little-endian
and big-endian mode, there should be no endian issues for the Ethernet
data. Big-endian software must still however be aware of the byte-
swapping effect when accessing the registers of the PCI-Ethernet device.

PCI-Graphics

The effects of byte swapping on big-endian software must be considered
by big-endian software.
Note

Universe's Involvement

Since PCI is little-endian and the VMEbus is big-endian, the Universe
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 and all devices connected directly to
VMEbus are expected to operate in big-endian mode, regardless of the
mode of operation in the processor's domain.
In big-endian mode, byte-swapping is performed by the Universe and then
by the Raven. The result has the desirable effect by being transparent to the
big-endian software.
In little-endian mode, however, software must be aware of the byte-
swapping effect from the Universe and the address reverse-rearranging
effect of the Raven.
There are graphics on the MVME3600 series boards, but no
graphics on the MVME2600/2700 series boards.
Endian Issues
5
5-15