System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-199
ID021414
Non-Confidential
To access the CPACR:
MRC p15,0,<Rt>,c1,c0,2 ; Read CPACR into Rt
MCR p15,0,<Rt>,c1,c0,2 ; Write Rt to CPACR
4.5.30
Secure Configuration Register
The SCR characteristics are:
Purpose
Defines the configuration of the current security state. It specifies:
•
The security state of the processor, Secure or Non-secure.
•
What state the processor branches to, if an IRQ, FIQ or external
abort occurs.
•
Whether the CPSR.F and CPSR.A bits can be modified when
SCR.NS = 1.
Usage constraints
This register is accessible as follows:
Any read or write to SCR in Secure EL1 state in AArch32 is trapped as an
exception to EL3.
Configurations
The SCR is a Restricted access register that exists only in the Secure state.
The SCR is mapped to the AArch64 SCR_EL3 register.
Attributes
SCR is a 32-bit register.
Figure 4-101
shows the SCR bit assignments.
Figure 4-101 SCR bit assignments
b. If the cp11 and cp10 fields are set to different values, the behavior is the same as if both fields were set to the value of cp10, in all respects
other than the value read back by explicitly reading cp11.
EL0
NS)
EL0
(S)
EL1
(NS)
EL1
(S)
EL2
EL3
(SCR.NS = 1)
EL3
(SCR.NS = 0)
-
-
-
RW
-
RW
RW
31
10 9 8 7 6
4 3 2 1 0
RES
0
SIF
HCE
FIQ
IRQ
NS
TWI
TWE
11
12
13
14
SCD
5
nET
EA
FW
AW
RES
0