Motorola MVME5100 Manual De Usuario
2-6
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Hawk PCI Host Bridge & Multi-Processor Interrupt Controller
2
PPC Address Mapping
The PHB will map either PCI memory space or PCI I/O space into PPC
address space using four programmable map decoders. These decoders
provide windows of access to the PCI bus from the PPC bus. The most
significant 16 bits of the PPC address are compared with the address range
of each map decoder, and if the address falls within the specified range, the
access is passed on to the PCI. An example of this is shown in
address space using four programmable map decoders. These decoders
provide windows of access to the PCI bus from the PPC bus. The most
significant 16 bits of the PPC address are compared with the address range
of each map decoder, and if the address falls within the specified range, the
access is passed on to the PCI. An example of this is shown in
.
Figure 2-2. PPC to PCI Address Decoding
There are no limits imposed by the PHB on how large of an address space
a map decoder can represent. There is a lower limit of a minimum of 64KB
due to the resolution of the address compare logic.
a map decoder can represent. There is a lower limit of a minimum of 64KB
due to the resolution of the address compare logic.
For each map, there is an associated set of attributes. These attributes are
used to enable read accesses, enable write accesses, enable write posting,
and define the PCI transfer characteristics.
used to enable read accesses, enable write accesses, enable write posting,
and define the PCI transfer characteristics.
PPC Bus Address
8 0 8 0 1 2 3 4
31
16
15
0
XSADDx Register
7 0 8 0 9 0 0 0
31
16
15
0
>=
<=
and
Decode is