System Control
ARM DDI 0500D
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4-209
ID021414
Non-Confidential
Table 4-201
shows the HSCTLR bit assignments.
Table 4-201 HSCTLR bit assignments
Bits
Name
Function
[31]
-
Reserved,
RES
0.
[30]
TE
Thumb Exception enable. This bit controls whether exceptions taken in Hyp mode are taken in A32 or T32
state:
0
Exceptions taken in A32 state.
1
Exceptions taken in T32 state.
[29:28]
-
Reserved,
RES
1.
[27:26]
-
Reserved,
RES
0.
[25]
EE
Exception Endianness. The value of this bit defines the value of the CPSR.E bit on entry to an exception
vector, including reset. This value also indicates the endianness of the translation table data for translation
table lookups:
0
Little endian.
1
Big endian.
[24]
-
Reserved,
RES
0.
[23:22]
-
Reserved,
RES
1.
[21]
FI
Fast Interrupts configuration enable bit. This bit can be used to reduce interrupt latency by disabling
implementation-defined performance features.
This bit is not implemented,
RES
0.
[20]
-
Reserved,
RES
0.
[19]
WXN
Write permission implies
Execute Never
(XN). This bit can be used to require all memory regions with write
permission to be treated as XN:
0
Regions with write permission are not forced to XN.
1
Regions with write permission are forced to XN.
The WXN bit is permitted to be cached in a TLB.
[18]
-
Reserved,
RES
1.
[17]
-
Reserved,
RES
0.
[16]
-
Reserved,
RES
1.
[15:13]
-
Reserved,
RES
0.
[12]
I
Instruction cache enable. This is an enable bit for instruction caches at EL2:
0
Instruction caches disabled at EL2. If HSCTLR.M is set to 0, instruction accesses from stage
1 of the EL2 translation regime are to Normal memory, Outer Shareable, Inner Non-cacheable,
Outer Non-cacheable.
1
Instruction caches enabled at EL2. If HSCTLR.M is set to 0, instruction accesses from stage
1 of the EL2 translation regime are to Normal memory, Outer Shareable, Inner Write-Through,
Outer Write-Through.
When this bit is 0, all EL2 Normal memory instruction accesses are Non-cacheable.
If this register is at the highest exception level implemented, field resets to 0. Otherwise, its reset value is
UNKNOWN
.