8-12
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part II. PowerPC Microprocessor Module
attempt to access these SPRs with a user-level program (MSR[PR] = 1) results in a
supervisor-level program exception.
The DC_CST register, shown in Figure 8-6, has an SPR encoding of 568.
Table 8-6 describes the bits of the DC_CST register.
BIT
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FIELD
DEN
DFWT
LES
Ñ
CMD
Ñ
CCER
1
CCER
2
CCER
3
Ñ
RESET
0
0
0
Ñ
Ñ
Ñ
0
0
0
Ñ
R/W
R
R
R
Ñ
R/W
Ñ
R
R
R
Ñ
BIT
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
FIELD
Ñ
RESET
Ñ
R/W
Ñ
SPR
568
Figure 8-6. Data Cache Control and Status Register (DC_CST)
Table 8-6. Data Cache Control and Status RegisterÑDC_CST
Bits
Name
Description
0
DEN
Data cache enable status
0
The data cache is disabled
1
The data cache is enabled
Note that this is a read-only bit. Any attempt to write to it is ignored. This bit is programmed by
issuing the appropriate command in DC_CST[CMD].
1
DFWT
Data cache forced write-through
0
The write-through behavior of the data cache is determined by the write-through
memory/cache access attribute (the W bit) in the MMU.
1
Writes to the data cache are forced to write through to memory.
Note that this is a read-only bit. Any attempt to write to it is ignored. This bit is programmed by
issuing the appropriate command in DC_CST[CMD].
2
LES
Little-endian swap
0
Used for big-endian (BE) and PowerPC little-endian (PPC-LE) modes. No modiÞcations to the
address or byte lanes are performed.
1
Used for true little-endian (TLE) mode. A 2-bit munge is performed on the physical address
before accessing the internal U-bus. Also, for accesses originating from the PowerPC core,
the SIU unmunges the address and swaps the bytes of data within each word at the external
bus/internal U-bus boundary.
See Appendix A, ÒByte Ordering,Ó for more information on MPC860 byte ordering. Note that this is
a read-only bit. Any attempt to write to it is ignored. This bit is programmed by issuing the
appropriate command in DC_CST[CMD].
3
Reserved
Содержание MPC860 PowerQUICC
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Страница 274: ...III iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part III Configuration ...
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Страница 325: ...MOTOROLA Part IV Hardware Interface IV v Part IV Hardware Interface ...
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