
2-18
G2 PowerPC Core Reference Manual
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MOTOROLA
Register Set
Figure 2-8. Required Physical Address Register (RPA)
Table 2-11 describes the bit settings of the RPA register.
2.1.2.8
BAT Registers (BAT4–BAT7)—G2_LE Only
The G2_LE MMU has four additional IBAT and four additional DBAT array entries that
provide a mechanism for translating additional blocks as large as 256 Mbytes from the
32-bit effective address space into the physical memory space. This can be used for
translating large address ranges whose mappings do not change frequently.
BATs are software-controlled arrays that store the available block address translations
on-chip. The G2_LE core supports block address translation through the use of two
independent instruction and data block address translation (IBAT and DBAT) arrays; each
array is comprised of four additional entries used for instruction accesses and four
additional entries used for data accesses.
IBAT4–IBAT7 and DBAT4–DBAT7 are implementation-specific registers on the G2_LE
core, which are optionally enabled in HID2. The format of these registers is the same as that
of IBAT0–IBAT3 and DBAT0–DBAT3. Each BAT array entry consists of a pair of BAT
registers—an upper and a lower BAT register for each entry. Figure 2-9 and Figure 2-10
show the format and bit definitions of the upper and lower BATs for 32-bit processor cores,
respectively.
Figure 2-9. Upper BAT Register
Table 2-11. RPA Bit Settings
Bits
Name
Description
0–19
RPN
Physical page number from PTE
20–22
—
Reserved
23
R
Referenced bit from PTE
24
C
Changed bit from PTE
25–28
WIMG
Memory/cache access attribute bits
29
—
Reserved
30–31
PP
Page protection bits from PTE
0
19 20
22
23 24 25
28 29 30 31
RPN
R
C
WIMG
PP
0 0 0
0
Reserved
BEPI
0 0 0 0
BL
Vs Vp
0
14 15
18 19
29 30 31
Reserved
F
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