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Cache
6-8
Freescale Semiconductor
6.3.2
Access Control Registers (ACR
n
)
The ACR
n
registers assign control attributes, such as cache mode and write protection, to specified
memory regions. ACR0 and ACR1 control data attributes; ACR2 and ACR3 control instruction attributes.
Registers are accessed with the MOVEC instruction with the Rc encodings in
.
For overlapping regions, the lower ACR number takes priority. Data transfers to and from these registers
are longword transfers.
NOTE
ACR0–3 are read/write by the debug module.
I
BDM: 0x004 (ACR0)
0x005 (ACR1)
0x006 (ACR2)
0x007 (ACR3)
Access: MOVEC write-only
Debug read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11
10
9
8
7
6
5
4
3
2
1
0
R
BA
ADMSK
E
S
0
0
AMM
0
0
0
CM
0
0
0
0
W
SP
Reset –
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
0
–
–
0
0
0
0
0
0
–
–
0
0
–
0
0
1
Reserved in ACR2 and ACR3
Figure 6-5. Access Control Register Format (ACR
n
)
Table 6-4. ACR
n
Field Descriptions
Field
Description
31–24
BA
Base address. Compared with address bits A[31:24]. Eligible addresses that match are assigned the access
control attributes.
23–16
ADMSK
Address mask. Setting a mask bit causes the corresponding address base bit to be ignored. The low-order mask
bits can be set to define contiguous regions larger than 16 Mbytes. The mask can define multiple non-contiguous
regions of memory.
15
E
Enable. Enables or disables the other ACR
n
bits.
0 Access control attributes disabled
1 Access control attributes enabled
14–13
S
Supervisor mode. Specifies whether only user or supervisor accesses are allowed in this address range or if the
type of access is a don’t care.
00 Match addresses only in user mode
01 Match addresses only in supervisor mode
1x Execute cache matching on all accesses
12–11
Reserved, must be cleared.
10
AMM
Address mask mode.
0 The ACR hit function allows control of a 16 Mbytes or greater memory region.
1 The upper 8 bits of the address and ACR are compared without a mask function. Address bits [23:20] of the
address and ACR are compared using ACR[19:16] as a mask, allowing control of a 1–16 Mbyte memory
region.
9–7
Reserved, must be cleared.
Содержание MCF54455
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