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Chapter 10. Memory Management Unit (MMU)
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10-21
MMU Implementation
Binary state bits are updated on all TLB write (load) operations as well as normal ITLB and
DTLB hits of non-locked entries. Also, if all entries in a binary state are locked, than that
state is always set. That is, if entries 15, 14, 13, and 12 were locked, LRU state bit
rdRecent15To14 is forced to one.
For a completely valid TLB, binary state information determines the LRU entry. The CF4e
replacement algorithm is deterministic and, for the case of a full TLB, with no locked
entries, and always touching new pages, the replacement entry repeats every 32 TLB loads.
10.6.3 TLB Locked Entries
Figure 10-11 is a ColdFire MMU Harvard TLB block diagram.
rdRecent07To04
A one indicates 07To04 is more recent than 03To00
rdRecent31To30
A one indicates 31To30 is more recent than 29To28
rdRecent27To26
A one indicates 27To26 is more recent than 25To24
rdRecent23To22
A one indicates 23To22 is more recent than 21To20
rdRecent19To18
A one indicates 19To18 is more recent than 17To16
rdRecent15To14
A one indicates 15To14 is more recent than 13To12
rdRecent11To10
A one indicates 11To10 is more recent than 09To08
rdRecent07To06
A one indicates 07To06 is more recent than 05To04
rdRecent03To02
A one indicates 03To02 is more recent than 01To00
rdRecent31
A one indicates 31 is more recent than 30
rdRecent29
A one indicates 29 is more recent than 28
rdRecent27
A one indicates 27 is more recent than 26
rdRecent25
A one indicates 25 is more recent than 24
rdRecent23
A one indicates 23 is more recent than 22
rdRecent21
A one indicates 21 is more recent than 20
rdRecent19
A one indicates 19 is more recent than 18
rdRecent17
A one indicates 17 is more recent than 16
rdRecent15
A one indicates 15 is more recent than 14
rdRecent13
A one indicates 13 is more recent than 12
rdRecent11
A one indicates 11 is more recent than 10
rdRecent09
A one indicates 09 is more recent than 08
rdRecent07
A one indicates 07 is more recent than 06
rdRecent05
A one indicates 05 is more recent than 04
rdRecent03
A one indicates 03 is more recent than 02
rdRecent01
A one indicates 01 is more recent than 00
Table 10-13. PLRU State Bits (Continued)
State Bits
Meaning
F
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n
.