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March 2002 Release
861
Virtex-II Pro™ Platform FPGA Documentation
1-800-255-7778
Memory Management
R
Memory Protection
The TLB entries defined by the PowerPC Book-E architecture support the following access
controls, which can be independently configured for privileged mode and user mode
accesses:
•
Execute
•
Read
•
Write
Software can use any combination of the access controls to manage memory protection.
For example, read/write access is specified by enabling both the read and write access
controls. No-access is specified by disabling both controls.
PowerPC 40x implementations control memory protection using a combination of fields in
the TLB entry and the zone-protection register (ZPR). These controls support many of the
same protection characteristics available in PowerPC Book-E processors, but not all of
them. For example, write-only protection cannot be specified.
Zone protection is not supported by the PowerPC Book-E architecture.
Memory Attributes
The PowerPC 40x family and PowerPC Book-E processors support the following memory
attributes:
•
Write through (W).
•
Caching inhibited (I).
•
Memory coherence (M). This attribute is not supported by the PPC405 and is ignored.
•
Guarded (G).
•
Endian (E).
•
User-defined. The PowerPC 40x family supports a single user-defined attribute (U0).
The PowerPC Book-E architecture supports up to four user-defined attributes (U0,
U1, U2, and U3).
All memory attributes supported by PowerPC 40x processors can be used in real mode
(address translation disabled) using storage-attribute control registers. These registers are
not supported by PowerPC Book-E processors.
Table F-5:
Summary of Memory Translation Extensions
Memory-Translation Feature
PowerPC 40x Family
6xx/7xx Family
Real mode
Supported
Unsupported
Virtual-address width
40 bits:
•
8-bit PID
•
32-bit effective address
97 bits:
•
1-bit instruction or data address-space
(from the MSR)
•
32-bit PID
•
64-bit effective address
Page size
1KB to 16MB
1KB to 1TB (terabyte)
TLB instructions
tlbia
tlbre
tlbsx[.]
tlbsync
tlbwe
tlbivax
tlbre
tlbsx[.]
tlbsync
tlbwe
Содержание Virtex-II Pro PPC405
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