C1.2.4
External access permissions to debug registers
External access permission to the debug registers is subject to the conditions at the time of the access.
The following table describes the core response to accesses through the external debug interface.
Table C1-1 External access conditions to registers
Name Condition
Description
Off
EDPRSR.PU is 0
Core power domain is completely off, or in a low-power state where the
core power domain registers cannot be accessed.
If debug power is off, then all external debug and memory-mapped register
accesses return an error.
DLK
DoubleLockStatus() == TRUE
(EDPRSR.DLK is 1)
OS Double Lock is locked.
OSLK
OSLSR_EL1.OSLK is 1
OS Lock is locked.
EDAD
AllowExternalDebugAccess() ==FALSE
External debug access is disabled. When an error is returned because of an
EDAD condition code, and this is the highest priority error condition,
EDPRSR.SDAD is set to 1. Otherwise SDAD is unchanged.
Default -
None of the conditions apply, normal access.
The following table shows an example of external register access condition codes for access to a
performance monitor register. To determine the access permission for the register, scan the columns from
left to right. Stop at the first column a condition is true, the entry gives the access permission of the
register and scanning stops.
Table C1-2 External register condition code example
Off DLK OSLK EDAD Default
-
-
-
-
RO
C1 Debug
C1.2 Debug register interfaces
100798_0300_00_en
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Summary of Contents for Cortex-A76 Core
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