Debug
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
11-5
ID021414
Non-Confidential
nPRESETDBG
This signal initializes the shared debug APB,
Cross Trigger Interface
(CTI), and
Cross Trigger Matrix
(CTM) logic. This maps to an external debug reset that
covers the resetting of the external debug interface and has no impact on the
processor functionality.
11.2.3
External access permissions
External access permission to the debug registers is subject to the conditions at the time of the
access.
Table 11-1
describe the processor response to accesses through the external debug
interface.
Table 11-2
shows an example of external register 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 11-1 External register conditions
Name
Condition
Description
Off
EDPRSR.PU is 0
Processor power domain is completely off, or in a low-power state where the
processor power domain registers cannot be accessed.
Note
If debug power is off then all external debug and memory-mapped register
accesses return an error.
DLK
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.
SLK
Memory-mapped interface only
Software lock is locked. For the external debug interface, ignore this column.
Default
-
None of the conditions apply, normal access.
Table 11-2 External register condition code example
Off
DLK
OSLK
EDAD
SLK
Default
-
-
-
-
RO/WI
RO