MVME5100 Single Board Computer Programmer's Reference Guide

Functional Description
Each map decoder also includes a programmable 16-bit address offset. The
offset is added to the 16 most significant bits of the PCI address, and the
result is used as the PPC address. This offset allows devices to reside at any
PPC address, independent of the PCI address map. An example of this is
shown in Figure 2-5.
PCI Bus Address 8 0 8 0 1 2 3 4
31
1615
0
PSOFFx Register 9 0 0 0
31
16
PPC Bus Address 1 0 8 0 1 2 3 4
0
1516
31
Figure 2-5. PCI to PPC Address Translation
All PHB address decoders are prioritized so that programming multiple
decoders to respond to the same address is not a problem. When the PCI
address falls into the range of more than one decoder, only the highest
priority one will respond. The decoders are prioritized as shown below.
Decoder Priority
PCI Slave 0 highest
PCI Slave 1
PCI Slave 2
PCI Slave 3 lowest
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