EPXA4 Datasheet, PDF (31/34 Pages) Altera Corporation – Excalibur Devices

A.3.3
Errata Sheet - Appendix A
Workarounds
There is no practical workaround for this erratum. This is due to the
difficulty in getting a debugging tool to recognise the symptoms of this
erratum and take the appropriate corrective action. However the
likelihood of failure with this mechanism is extremely low and the impact
of failure is also low as it affects debugging operations only, therefore
there is no plan to revise the design to resolve this erratum.
Data Abort and Watchpoint with Breakpoint Following
(ARM9TDMI–10)—Category 2
Summary
The processor may fail to execute the abort handler if a data abort occurs
on a watchpointed instruction and a breakpoint is in the execution
pipeline.
Conditions
The conditions for this erratum are:
1. An instruction that causes both a Data Abort and a watchpoint to
occur and
2. The execution of the following instruction will cause a breakpoint to
occur
1
There should be no data dependency between the two
instructions such that a pipeline interlock occurs. If there is such
data dependency then the processor behaves correctly.
If the above conditions are met then the Data Abort may be missed.
Implications
In this erratum Data Abort entry is halted by debug entry and this causes
the state indicating a Data Abort to be lost on return from debug. Hence
the Data Abort handler will fail to be invoked. This may result in
unintended or unpredictable device behaviour.
Altera Corporation
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