Functional Description
128
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Cortex-M4 Peripherals
shows the cache policy for memory attribute encodings with a TEX value in the range of 0x4 to
0x7.
Table 2-4. Cache Policy for Memory Attribute Encoding
Encoding,
AA or BB
Corresponding Cache Policy
00
Noncacheable
01
Write back, write and read allocate
10
Write through, no write allocate
11
Write back, no write allocate
shows the AP encodings in the MPUATTR register that define the access permissions for
privileged and unprivileged software.
Table 2-5. AP Bit Field Encoding
AP Bit Field
Privileged
Permissions
Unprivileged
Permissions
Description
000
No access
No access
All accesses generate a permission fault.
001
RW
No access
Access from privileged software only.
010
RW
RO
Writes by unprivileged software generate a permission fault.
011
RW
RW
Full access.
100
Unpredictable
Unpredictable
Reserved.
101
RO
No access
Reads by privileged software only.
110
RO
RO
Read-only, by privileged or unprivileged software.
111
RO
RO
Read-only, by privileged or unprivileged software.
2.2.4.2.1 MPU Configuration for a MSP432E4 Microcontroller
MSP432E4 microcontrollers have only a single processor and no caches. As a result, the MPU should be
programmed as shown in
Table 2-6. Memory Region Attributes for MSP432E4 Microcontrollers
Memory Region
TEX
S
C
B
Memory Type and Attributes
Flash memory
000b
0
1
0
Normal memory, nonshareable, write-through
Internal SRAM
000b
1
1
0
Normal memory, shareable, write-through
External SRAM
000b
1
1
1
Normal memory, shareable, write-back, write-allocate
Peripherals
000b
1
0
1
Device memory, shareable
In current MSP432E4 microcontroller implementations, the shareability and cache policy attributes do not
affect the system behavior. However, using these settings for the MPU regions can make the application
code more portable. The values given are for typical situations.
2.2.4.3
MPU Mismatch
When an access violates the MPU permissions, the processor generates a memory management fault.
For more information, see
. The MFAULTSTAT register indicates the cause of the fault. For
more information, see
.
2.2.5 Floating-Point Unit (FPU)
This section describes the Floating-Point Unit (FPU) and the registers it uses. The FPU provides:
•
32-bit instructions for single-precision (C float) data-processing operations
•
Combined multiply and accumulate instructions for increased precision (Fused MAC)