Debug
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
10-18
ID073015
Non-Confidential
3.
Poll the DSCR or Authentication Status Register to check whether the processor has
already detected the changed value of these signals. This is required because the system
might not issue the signal change to the processor until several cycles after the DSB
completes.
4.
Perform an
ISB
, an Exception entry, or Exception exit.
The software cannot perform debug or analysis operations that depend on the new value of the
authentication signals until this procedure is complete. The same rules apply when the debugger
has control of the processor through the ITR while in debug state.
The relevant combinations of the
DBGEN
,
NIDEN
,
SPIDEN
, and
SPNIDEN
values can be
determined by polling DSCR[17:16], DSCR[15:14], or the Authentication Status Register.
10.8.4
Debug APB Interface
Use the Debug APB interface to access:
•
•
debug management registers in
10.8.5
External debug request interface
The following sections describe the external debug request interface signals:
•
•
•
•
•
EDBGRQ
This signal generates a halting debug event, to request the processor to enter debug state. When
this occurs, the DSCR[5:2] method of debug entry bits are set to b0100. When
EDBGRQ
is
asserted, it must be held until
DBGACK
is asserted. Failure to do so leads to
UNPREDICTABLE
behavior of the processor.
DBGACK
The processor asserts
DBGACK
to indicate that the system has entered debug state. It serves as
a handshake for the
EDBGRQ
signal. The
DBGACK
signal is also driven HIGH when the
debugger sets the DSCR[10] DbgAck bit to 1.
DBGCPUDONE
DBGCPUDONE
is asserted when the processor has completed a DSB as part of the entry
procedure to debug state.
The processor asserts
DBGCPUDONE
only after it has completed all Non-debug state memory
accesses. Therefore the system can use
DBGCPUDONE
as an indicator that all memory
accesses issued by the processor result from operations performed by a debugger.
shows the Cortex-A9 connections specific to debug request and
restart.