ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Debug Events
Interaction of IVA mismatch breakpoints with other breakpoints and Vector Catch
When a BRPn is programmed for IVA mismatch and does not generate a Breakpoint debug event because
the general conditions specified in DBGBCRn are not met, this does not affect the generation of:
Breakpoint debug events by other BRPs
Vector Catch debug events.
Note
In this context, the general conditions specified in DBGBCR not being met means that at least one of the
following applies:
the BRP is not enabled
the Privileged mode control bits of the DBGBCR do not match the mode of the processor
DBGBCR is configured for linked Context ID matching but the linked BRP either is not enabled or
does not match the current Context ID
the Security Extensions are implemented, and the Security state control field of DBGBCR does not
match the security state of the processor.
However, if the general conditions specified in DBGBCRn are met, and BRPn does not generate a
Breakpoint debug event only because the IVA fails the comparison required for an IVA mismatch, then the
failure of this comparison can affect the generation of other debug events:
if any other BRP, BRPm, hits on its required comparison with the IVA and meets the general
conditions specified in DBGBCRm, it is UNPREDICTABLE whether BRPm generates a Breakpoint
debug event
if the Vector Catch Register defines a Vector Catch that matches the IVA, it is UNPREDICTABLE
whether a Vector Catch debug event is generated.
Generation of IVA mismatch breakpoints on branch to self instructions
This section describes the generation of Breakpoint debug events when the IVA of an instruction that
branches to itself misses a BRP programmed for IVA mismatch, and all the general conditions specified in
the DBGBCR are met. See the IVA mismatch column of Table C10-11 on page C10-56 for details of when
an IVA mismatch comparison misses. In this case:
1. The first time the instruction is committed for execution the BRP does not generate a Breakpoint
debug event.
2. Because the instruction branches to itself, if no exception is generated, the instruction is committed
for execution again. On this and any subsequent execution, it is UNPREDICTABLE whether the BRP
generates a Breakpoint debug event.
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