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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
758 of 808
NXP Semiconductors
UM10360
Chapter 34: Appendix: Cortex-M3 User Guide
4.5.2 MPU Control Register
The MPU CTRL register:
•
enables the MPU
•
enables the default memory map background region
•
enables use of the MPU when in the hard fault,
Non-maskable Interrupt
(NMI), and
FAULTMASK escalated handlers.
See the register summary in
for the MPU CTRL attributes. The bit
assignments are shown in
When ENABLE and PRIVDEFENA are both set to 1:
[15:8]
DREGION
Indicates the number of supported MPU data regions:
0x08
= Eight MPU regions.
[7:0]
- Reserved.
[0]
SEPARATE
Indicates support for unified or separate instruction and
date memory maps:
0 = unified.
Table 653. TYPE register bit assignments
Bits
Name
Function
Table 654. MPU CTRL register bit assignments
Bits
Name
Function
[31:3]
- Reserved.
[2]
PRIVDEFENA
Enables privileged software access to the default memory map:
0 = If the MPU is enabled, disables use of the default memory map.
Any memory access to a location not covered by any enabled
region causes a fault.
1 = If the MPU is enabled, enables use of the default memory map
as a background region for privileged software accesses.
When enabled, the background region acts as if it is region number
-1. Any region that is defined and enabled has priority over this
default map.
If the MPU is disabled, the processor ignores this bit.
[1]
HFNMIENA
Enables the operation of MPU during hard fault, NMI, and
FAULTMASK handlers.
When the MPU is enabled:
0 = MPU is disabled during hard fault, NMI, and FAULTMASK
handlers, regardless of the value of the ENABLE bit
1 = the MPU is enabled during hard fault, NMI, and FAULTMASK
handlers.
When the MPU is disabled, if this bit is set to 1 the behavior is
Unpredictable.
[0]
ENABLE
Enables the MPU:
0 = MPU disabled
1 = MPU enabled.