System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-64
ID021414
Non-Confidential
[14]
TWE
Traps
WFE
instruction if it would cause suspension of execution. For example, if there is no pending WFE event.
The possible values are:
0
WFE
instruction is not trapped. This is the reset value.
1
WFE
instruction executed in Non-secure EL1 or EL0 is trapped to EL2 for AArch32 and AArch64
Execution states.
[13]
TWI
Traps
WFI
instruction if it causes suspension of execution. For example, if there is no pending WFI event. The
possible values are:
0
WFI
instruction is not trapped. This is the reset value.
1
WFI
instruction executed in Non-secure EL1 or EL0 is trapped to EL2 for AArch32 and AArch64
Execution states.
[12]
DC
Default cacheable. When this bit is set it causes:
•
SCTLR_EL1.M to behave as 0 for all purposes other than reading the bit.
•
HCR_EL2.VM to behave as 1 for all purposes other than reading the bit.
The memory type produced by the first stage of translation in Non-secure EL1 and EL0 is Non-Shareable, Inner
Write-Back Write-Allocate, Outer Write-Back Write-Allocate. The reset value is
0
.
[11:10]
BSU
Barrier shareability upgrade. Determines the minimum shareability domain that is supplied to any barrier
executed from Non-secure EL1 or EL0. The possible values are:
0b00
No effect. This is the reset value.
0b01
Inner Shareable.
0b10
Outer Shareable.
0b11
Full system.
This value is combined with the specified level of the barrier held in its instruction, according to the algorithm
for combining shareability attributes.
Table 4-72 HCR_EL2 bit assignments (continued)
Bits
Name
Function