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Programming Considerations
6. When the MVME1603/MVME1604 is operating as the VMEbus
System Controller, an HRESET∗ signal will also cause a VMEbus
SYSRESET∗.
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Endian Issues
The MVME1603/MVME1604 supports both little-endian (e.g. Windows
NT) and big-endian software (e.g. AIX). The PowerPC processor and the
VMEbus are inherently big-endian, while the PCI bus is inherently littleendian. The following figures illustrate how the MVME1603/MVME1604
handles the endian issue in big-endian and little-endian modes:
Processor/Memory Domain
The MPC603/604 processor can operate in both big-endian and littleendian mode. However, it always treats the external processor/memory
bus as big-endian by performing address rearrangement and reordering
when running in little-endian mode.
Role of the MPC105
Because the PCI bus is little-endian, the MPC105 performs byte swapping
in both directions (from PCI to memory and from the processor to PCI) to
maintain address invariance while programmed to operate in big-endian
mode with the processor and the memory subsystem.
In little-endian mode, the MPC105 reverse-rearranges the address for
PCI-bound accesses and rearranges the address for memory-bound
accesses (from PCI). In this case, no byte swapping is done.
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