
DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
761 of 808
NXP Semiconductors
UM10360
Chapter 34: Appendix: Cortex-M3 User Guide
For information about access permission, see
4.5.5.1
SIZE field values
The SIZE field defines the size of the MPU memory region specified by the RNR. as
follows:
(Region size in bytes) = 2
(SIZE+1)
The smallest permitted region size is 32B, corresponding to a SIZE value of 4.
gives example SIZE values, with the corresponding region size and value of
N in the RBAR.
[1]
In the RBAR, see
Table 657. RASR bit assignments
Bits
Name
Function
[31:29]
-
Reserved.
[28]
XN
Instruction access disable bit:
0 = instruction fetches enabled
1 = instruction fetches disabled.
[27]
-
Reserved.
[26:24]
AP
Access permission field, see
.
[23:22]
-
Reserved.
[21:19, 17, 16]
TEX, C, B
Memory access attributes, see
.
[18]
S
Shareable bit, see
[15:8]
SRD
Subregion disable bits. For each bit in this field:
0 = corresponding sub-region is enabled
1 = corresponding sub-region is disabled
Region sizes of 128 bytes and less do not support subregions.
When writing the attributes for such a region, write the SRD field as
0x00
.
[7:6]
-
Reserved.
[5:1]
SIZE
Specifies the size of the MPU protection region. The minimum
permitted value is 3 (b00010), see See
for more
information.
[0]
ENABLE
Region enable bit.
Table 658. Example SIZE field values
SIZE value
Region size
Value of N
Note
b00100 (4)
32B
5
Minimum permitted
size
b01001 (9)
1KB
10
-
b10011 (19)
1MB
20
-
b11101 (29)
1GB
30
-
b11111 (31)
4GB
b01100
Maximum possible size