EPXA4 Datasheet, PDF (32/34 Pages) Altera Corporation – Excalibur Devices

Errata Sheet - Appendix A
A.3.4
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.
Watchpoint coincident with Debug Request (ARM9TDMI–11)—
Category 2
Summary
The processor can falsely exit debug state and continue execution if
EDBGRQ or the scan chain created debug request is asserted whilst
debug entry is occurring.
Conditions
A combination of two conditions is required to cause this erratum:
1. Debug request is asserted and
2. An instruction that generates a watchpoint is executing
If the above conditions are met then the debug entry mechanism fails to
behave in the defined manner and the device may return from debug and
execute from the incorrect address.
Implications
In this erratum, the debug request takes affect before the complete
recognition of the watchpoint. This may result in unreliable debug entry,
the watchpoint being missed and premature exit of debug state. Thus
unintended or unpredictable device behaviour may result.
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.
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Altera Corporation