Section 3 Memory Management Unit (MMU)
Rev. 5.00 May 29, 2006 page 63 of 698
REJ09B0146-0500
31
16
11
12
17
0
Virtual address
Ways 0 to 3
VPN(31–17)
VPN(11, 10)
ASID(7–0)
V
0
Address array
Data array
PPN(31–10) PR(1, 0) SZ
C
D
SH
Index
31
Figure 3.6 TLB Indexing (IX = 0)
3.3.3
TLB Address Comparison
The results of address comparison determine whether a specific virtual page number is registered
in the TLB. The virtual page number of the virtual address that accesses external memory is
compared to the virtual page number of the indexed TLB entry. The ASID within the PTEH is
compared to the ASID of the indexed TLB entry. All four ways are searched simultaneously. If the
compared values match, and the indexed TLB entry is valid (V bit
=
1), the hit is registered.
It is necessary to have software ensure that TLB hits do not occur simultaneously in more than one
way, as hardware operation is not guaranteed if this occurs. For example, if there are two identical
TLB entries with the same VPN and a setting is made such that a TLB hit is made only by a
process with ASID = H'FF when one is in the shared state (SH = 1) and the other in the non-shared
state (SH = 0), then if the ASID in PTEH is set to H'FF, there is a possibility of simultaneous TLB
hits in both these ways. It is therefore necessary to ensure that this kind of setting is not made by
software.
The object compared varies depending on the page management information (SZ, SH) in the TLB
entry. It also varies depending on whether the system supports multiple virtual memory or single
virtual memory.
The page-size information determines whether VPN (11, 10) is compared. VPN (11, 10) is
compared for 1-kbyte pages (SZ = 0) but not for 4-kbyte pages (SZ = 1).
The sharing information (SH) determines whether the PTEH.ASID and the ASID in the TLB entry
are compared. ASIDs are compared when there is no sharing between processes (SH
=
0) but not
when there is sharing (SH
=
1).
Summary of Contents for SH7706 Series
Page 8: ...Rev 5 00 May 29 2006 page viii of xlviii ...
Page 160: ...Section 5 Cache Rev 5 00 May 29 2006 page 112 of 698 REJ09B0146 0500 ...
Page 370: ...Section 11 Watchdog Timer WDT Rev 5 00 May 29 2006 page 322 of 698 REJ09B0146 0500 ...
Page 554: ...Section 17 Pin Function Controller PFC Rev 5 00 May 29 2006 page 506 of 698 REJ09B0146 0500 ...
Page 576: ...Section 18 I O Ports Rev 5 00 May 29 2006 page 528 of 698 REJ09B0146 0500 ...
Page 746: ...Index Rev 5 00 May 29 2006 page 698 of 698 REJ09B0146 0500 ...
Page 749: ...SH7706 Group Hardware Manual ...