Pci Domain; Vmebus Domain - Motorola MVME1603 Installation And Use Manual

PCI Domain

The PCI bus is inherently little-endian and all devices connected directly
to PCI will operate in little-endian mode, regardless of the mode of
operation in the processor's domain.
53C825 or 53C810(SCSI)
SCSI is 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 MPC105 maintains address invariance in both little-endian and
big-endian mode, there should be no endian issues for the SCSI data. Big-
endian software must still be aware of the byte-swapping effect when
accessing the registers of the 53C825 or 53C810, however.
DEC21040 (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 MPC105 maintains address invariance in both little-endian and
big-endian mode, there should be no endian issues for the Ethernet data.
Big-endian software must still be aware of the byte-swapping effect when
accessing the registers of the DEC21040, however.
GD5446 (Graphics)
Big-endian graphic software must take the effects of byte-swapping on
big-endian software into account.
Role of the VME2PCI
Because PCI is little-endian and the VMEbus is big-endian, the VME2PCI
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 are expected to operate in big-endian mode, regardless of the
mode of operation in the processor's domain.
Operating Instructions
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