
Chapter 8. Local Memory
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8-49
Cache Overview
Table 8-29 describes ACR
n
fields.
I
31
24 23
16 15 14 13 12 11
10
9
7
6
5
4
3
2
1
0
Field
Address Base
Address Mask
E
S
—
AMM
—
CM
SP
W
1
—
Reset
Uninitialized
0
Uninitialized
R/W
Write (R/W by debug module)
Rc
ACR0: 0x004; ACR1: 0x005; ACR2: 0x006; ACR3: 0x007
1
Reserved in ACR2 and ACR3.
Figure 8-17. Access Control Register Format (ACR
n
)
Table 8-29. ACR
n
Field Descriptions
Bits
Name
Description
31–24
Address
base
Address base. Compared with address bits A[31:24]. Eligible addresses that match are
assigned the access control attributes of this register.
23–16
Address
mask
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 noncontiguous 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, should 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; should be cleared.
6–5
CM
Cache mode. Selects the cache mode and access precision. Precise and imprecise modes are
described in Section 8.7.5, “Cache-Inhibited Accesses.”
00 Cacheable, write-through
01 Cacheable, copyback
10 Cache-inhibited, precise
11 Cache-inhibited, imprecise
4
—
Reserved, should be cleared.
3
SP
Supervisor protect.
0 Indicates supervisor and user mode access allowed, reset value is 0
1 Indicates only supervisor access is allowed to this address space and attempted user mode
accesses generate an access error exception
F
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n
.