TM4C129EKCPDT Datasheet, PDF (145/2012 Pages) Texas Instruments – Tiva Microcontroller

Tiva^™ TM4C129EKCPDT Microcontroller
3.1.4.1
Table 3-2 on page 145 shows the possible MPU region attributes. See the section called “MPU
Configuration for a Tiva™ C Series Microcontroller” on page 149 for guidelines for programming a
microcontroller implementation.
Table 3-2. Memory Attributes Summary
Memory Type
Strongly Ordered
Device
Normal
Description
All accesses to Strongly Ordered memory occur in program order.
Memory-mapped peripherals
Normal memory
To avoid unexpected behavior, disable the interrupts before updating the attributes of a region that
the interrupt handlers might access.
Ensure software uses aligned accesses of the correct size to access MPU registers:
■ Except for the MPU Region Attribute and Size (MPUATTR) register, all MPU registers must
be accessed with aligned word accesses.
■ The MPUATTR register can be accessed with byte or aligned halfword or word accesses.
The processor does not support unaligned accesses to MPU registers.
When setting up the MPU, and if the MPU has previously been programmed, disable unused regions
to prevent any previous region settings from affecting the new MPU setup.
Updating an MPU Region
To update the attributes for an MPU region, the MPU Region Number (MPUNUMBER), MPU
Region Base Address (MPUBASE) and MPUATTR registers must be updated. Each register can
be programmed separately or with a multiple-word write to program all of these registers. You can
use the MPUBASEx and MPUATTRx aliases to program up to four regions simultaneously using
an STM instruction.
Updating an MPU Region Using Separate Words
This example simple code configures one region:
; R1 = region number
; R2 = size/enable
; R3 = attributes
; R4 = address
LDR R0,=MPUNUMBER
STR R1, [R0, #0x0]
STR R4, [R0, #0x4]
STRH R2, [R0, #0x8]
STRH R3, [R0, #0xA]
; 0xE000ED98, MPU region number register
; Region Number
; Region Base Address
; Region Size and Enable
; Region Attribute
Disable a region before writing new region settings to the MPU if you have previously enabled the
region being changed. For example:
; R1 = region number
; R2 = size/enable
; R3 = attributes
; R4 = address
LDR R0,=MPUNUMBER
; 0xE000ED98, MPU region number register
June 18, 2014
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