Datasheet

203
SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
10.23.4 MPU Region Base Address Register
The RBAR defines the base address of the MPU region selected by the RNR, and can update the value of the
RNR. See the register summary in Table 10-35 on page 198 for its attributes.
Write RBAR with the VALID bit set to 1 to change the current region number and update the RNR. The bit
assignments are:
•ADDR
Region base address field. The value of N depends on the region size. For more information see “The ADDR field” .
•VALID
MPU Region Number valid bit:
Write:
0: RNR not changed, and the processor:
updates the base address for the region specified in the RNR
ignores the value of the REGION field
1: the processor:
updates the value of the RNR to the value of the REGION field
updates the base address for the region specified in the REGION field.
Always reads as zero.
•REGION
MPU region field:
For the behavior on writes, see the description of the VALID field.
On reads, returns the current region number, as specified by the RNR.
10.23.4.1 The ADDR field
The ADDR field is bits[31:N] of the RBAR. The region size, as specified by the SIZE field in the RASR, defines the
value of N:
N = Log
2
(Region size in bytes),
If the region size is configured to 4GB, in the RASR, there is no valid ADDR field. In this case, the region occupies
the complete memory map, and the base address is 0x00000000.
The base address is aligned to the size of the region. For example, a 64KB region must be aligned on a multiple of
64KB, for example, at 0x00010000 or 0x00020000.
31 302928 27 26 25 24
ADDR
23 22 21 20 19 18 17 16
ADDR
15 14 13 12 11 10 9 N
ADDR
N-16543 210
Reserved VALID REGION