72
3.3.4
Page Management Information
In addition to the SH and SZ bits, the page management information of TLB entries also includes
D, C, and PR bits.
The D bit of a TLB entry indicates whether the page is dirty (i.e., has been written to). If the D bit
is 0, an attempt to write to the page results in an initial page write exception. For physical page
swapping between secondary memory and main memory, for example, pages are controlled so that
a dirty page is paged out of main memory only after that page is written back to secondary
memory.
The C bit in the entry indicates whether the referenced page resides in a cacheable or non-
cacheable area of memory. When the control register in area 1 is mapped, set the C bit to 0. The
PR field specifies the access rights for the page in privileged and user modes and is used to protect
memory. Attempts at nonpermitted accesses result in TLB protection violation exceptions.
Access states designated by the D, C, and PR bits are shown in table 3.2.
Table 3.2
Access States Designated by D, C, and PR Bits
Privileged Mode
User Mode
Reading
Writing
Reading
Writing
D bit
0
Permitted
Initial page write
exception
Permitted
Initial page write
exception
1
Permitted
Permitted
Permitted
Permitted
C bit
0
Permitted
(no caching)
Permitted
(no caching)
Permitted
(no caching)
Permitted
(no caching)
1
Permitted
(with caching)
Permitted
(with caching)
Permitted
(with caching)
Permitted
(with caching)
PR bit
00
Permitted
TLB protection
violation exception
TLB protection
violation
exception
TLB protection
violation exception
01
Permitted
Permitted
TLB protection
violation
exception
TLB protection
violation exception
10
Permitted
TLB protection
violation exception
Permitted
TLB protection
violation exception
11
Permitted
Permitted
Permitted
Permitted
Содержание SH7709S
Страница 2: ...Hitachi SuperH RISC engine SH7709S Hardware Manual ADE 602 250 Rev 1 0 09 21 01 Hitachi Ltd ...
Страница 75: ...56 ...
Страница 107: ...88 ...
Страница 125: ...106 ...
Страница 139: ...120 ...
Страница 203: ...184 ...
Страница 245: ...226 ...
Страница 292: ...273 T1 CKIO A25 to A0 CSn RD WR RD D31 to D0 WEn D31 to D0 BS T2 Read Write Figure 10 6 Basic Timing of Basic Interface ...
Страница 323: ...304 Tp TRr TRrw TRrw CKIO CKE CSn RAS3U RAS3L CASU CASL RD WR Figure 10 28 Synchronous DRAM Auto Refresh Timing ...
Страница 411: ...392 ...
Страница 609: ...590 ...
Страница 635: ...616 ...
Страница 663: ...644 ...
Страница 679: ...660 ...