System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-203
ID021414
Non-Confidential
Any read or write to NSACR in Secure EL1 state in AArch32 is trapped
as an exception to EL3.
Configurations
There is one copy of this register that is used in both Secure and
Non-secure states.
If EL3 is using AArch64, then any reads of the NSACR from Non-secure
EL2 or Non-secure EL1 using AArch32 return a fixed value of
0x00000C00
.
In AArch64, the NSACR functionality is replaced by the behavior in
CPTR_EL3.
Attributes
NSACR is a 32-bit register.
Figure 4-103
shows the NSACR bit assignments.
Figure 4-103 NSACR bit assignments
Table 4-198
shows the NSACR bit assignments.
Note
If the values of the cp11 and cp10 fields are not the same, the behavior is
UNPREDICTABLE
.
31
16 15 14
12 11 10 9
0
RES
0
RES
0
NSASEDIS
Reserved
cp10
cp11
RES
0
Table 4-198 NSACR bit assignments
Bits
Name
Function
[31:16]
-
Reserved,
RES
0.
[15]
NSASEDIS
Disable Non-secure Advanced SIMD functionality:
0
This bit has no effect on the ability to write CPACR.ASEDIS, this is the reset value.
1
When executing in Non-secure state, the CPACR.ASEDIS bit has a fixed value of 1 and
writes to it are ignored.
If Advanced SIMD and Floating-point are not implemented, this bit is
RES
0.
[14:12]
-
Reserved,
RES
0.
[11]
cp11
Non-secure access to CP11 enable:
0
Secure access only. Any attempt to access CP11 in Non-secure state results in an Undefined
Instruction exception. If the processor is in Non-secure state, the corresponding bits in the
CPACR ignore writes and read as
0b00
, access denied. This is the reset value.
1
Secure or Non-secure access.
If Advanced SIMD and Floating-point are not implemented, this bit is
RES
0.
[10]
cp10
Non-secure access to CP10 enable:
0
Secure access only. Any attempt to access CP10 in Non-secure state results in an Undefined
Instruction exception. If the processor is in Non-secure state, the corresponding bits in the
CPACR ignore writes and read as
0b00
, access denied. This is the reset value.
1
Secure or Non-secure access.
If Advanced SIMD and Floating-point are not implemented, this bit is
RES
0.
[9:0]
-
Reserved,
RES
0.