10. Endian Mapping
179
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
10.3
Processor Bus and PowerSpan II Register Transfers
The PowerSpan II PB Slave supports register accesses from a PowerPC operating in big-endian or
PowerPC little-endian mode. The endian conversion mode for processor access to PowerSpan II
registers is selected by programming the END bit in the
“Processor Bus Register Image Base Address
. The default mode is big-endian, which matches the default mode of the
processor bus.
PowerSpan II registers are little-endian structures. The endian conversion process provided by
PowerSpan II for processor bus accesses to its registers is designed to preserve the significance of the
programmer’s multi-byte structures or scalars. Endian conversion for access to PowerSpan II registers
from the processor is data invariant.
When the processor bus is operating in big-endian mode, the END bit must be set to big-endian mode.
In this case, the PowerSpan II PB slave maps the processor bus byte lanes to PowerSpan II register
addresses according to
.