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Functional Description
127
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Cortex-M4 Peripherals
2.2.4.1.3.1 Example of SRD Use
Two regions with the same base address overlap. Region one is 128 KB, and region two is 512 KB. To
ensure the attributes from region one apply to the first 128 KB region, configure the SRD field for region
two to 0x03 to disable the first two subregions, as
shows.
Figure 2-1. SRD Use Example
2.2.4.2
MPU Access Permission Attributes
The access permission bits, TEX, S, C, B, AP, and XN of the MPUATTR register, control access to the
corresponding memory region. If an access is made to an area of memory without the required
permissions, then the MPU generates a permission fault.
shows the encodings for the TEX, C, B, and S access permission bits. All encodings are shown
for completeness, however the current implementation of the Cortex-M4 does not support the concept of
cacheability or shareability. For information on programming the MPU for MSP432E4 implementations,
see
.
(1)
The MPU ignores the value of this bit.
Table 2-3. TEX, S, C, and B Bit Field Encoding
TEX
S
C
B
Memory Type
Shareability
Other Attributes
000b
x
(1)
0
0
Strongly Ordered
Shareable
–
000
x
(1)
0
1
Device
Shareable
–
000
0
1
0
Normal
Not shareable
Outer and inner write-through. No
write allocate.
000
1
1
0
Normal
Shareable
000
0
1
1
Normal
Not shareable
000
1
1
1
Normal
Shareable
001
0
0
0
Normal
Not shareable
Outer and inner noncacheable.
001
1
0
0
Normal
Shareable
001
x
(1)
0
1
Reserved
encoding
–
–
001
x
(1)
1
0
Reserved
encoding
–
–
001
0
1
1
Normal
Not shareable
Outer and inner write-back. Write and
read allocate.
001
1
1
1
Normal
Shareable
010
x
(1)
0
0
Device
Not shareable
Nonshared Device.
010
x
(1)
0
1
Reserved
encoding
–
–
010
x
(1)
1
x
(1)
Reserved
encoding
–
–
1BB
0
A
A
Normal
Not shareable
Cached memory (BB = outer policy,
AA = inner policy).
See
for the encoding of the
AA and BB bits.
1BB
1
A
A
Normal
Shareable