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Memory Management Unit
e200z3 Power Architecture Core Reference Manual, Rev. 2
Freescale Semiconductor
5-7
Figure 5-3. Granting of Access Permission
5.3
Translation Lookaside Buffer
The EIS architecture defines support for zero or more TLBs in an implementation, each with its own
characteristics, and provides configuration information for software to query the existence and structure
of TLBs through a set of SPRs—MMUCFG, TLB0CFG, TLB1CFG, and so on. By convention, TLB0 is
used for a set-associative TLB with fixed page sizes, TLB1 is used for a fully-associative TLB with
variable page sizes, and TLB2 is arbitrarily defined by an implementation. The e200z3 MMU supports a
single TLB that is fully associative and supports variable page sizes; thus it corresponds to TLB1 in the
programming model. For the rest of this document, TLB, TLBCAM, and TLB1 are used interchangeably.
The TLB on the e200z3 MMU (TLB1) consists of a 16-entry, fully-associative content-addressable
memory (CAM) array with support for nine page sizes. To perform a lookup, the TLB is searched in
parallel for a matching TLB entry. The contents of a matching TLB entry are then concatenated with the
page offset of the original effective address. The result constitutes the real (physical) address of the access.
A hit to multiple TLB entries is considered to be a programming error. If this occurs, the TLB generates
an invalid address and TLB entries may be corrupted (an exception will not be reported).
Access Granted
Instruction Fetch
MSR[PR]
TLB_entry[UX]
TLB_entry[SX]
Load-Class Data Access
TLB_entry[UR]
TLB_entry[SR]
Store-Class Data Access
TLB_entry[UW]
TLB_entry[SW]
TLB Match (see
Содержание e200z3
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