K60P100M100SF2RM Datasheet, PDF (395/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 18 Memory Protection Unit (MPU)
1. If the access does not hit in any region descriptor, a protection error is reported.
2. If the access hits in a single region descriptor and that region signals a protection
violation, a protection error is reported.
3. If the access hits in multiple (overlapping) regions and all regions signal protection
violations, a protection error is reported.
As shown in the third condition, granting permission is a higher priority than denying
access for overlapping regions. This approach is more flexible to system software in
region descriptor assignments. For an example of the use of overlapping region
descriptors, see Application Information.
18.4.3 Power Management
Disabling the MPU by clearing CESR[VLD] minimizes power dissipation. To minimize
the power dissipation of an enabled MPU, invalidate unused region descriptors by
clearing the associated RGDn_Word3[VLD] bits.
18.5 Initialization Information
At system startup, load the appropriate number of region descriptors, including setting
RGDn_Word3[VLD]. Setting CESR[VLD] enables the module.
If the system requires that all the loaded region descriptors be enabled simultaneously,
first ensure that the entire MPU is disabled (CESR[VLD]=0).
Note
A region descriptor must be set to allow access to the MPU
registers if further changes are needed.
18.6 Application Information
In an operational system, interfacing with the MPU is generally classified into the
following activities:
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
395