EPXA4 Datasheet, PDF (9/34 Pages) Altera Corporation – Excalibur Devices

A.2
A.2.1
Errata Sheet - Appendix A
Errata for the ETM9 Trace Module
See Table 1 on page 7 and associated text for an explanation of
categorisation.
Invalid data trace following FIFO overflow—Category 1
Note: ARM has updated the errata classifications. This is a category 1
erratum under the previous definition, which was:
‘Features which it is impossible, or very hard, to work around and are
likely to affect use of this device.’
Description
The Embedded Trace Macrocell (ETM) contains a small FIFO which under
some circumstances can overflow, leading to the loss of trace. This is
normal behavior.
However, if the FIFO overflows during an extended wait-state period
while attempting to capture data trace from a block data transfer
instruction, then the data trace can become invalid.
When trace is resumed:
■ Data values traced may be invalid until the next indirect branch.
■ Data addresses traced may be invalid until the next trace gap, or the
next periodic synchronization point.
■ Instruction trace is unaffected.
An example of how exactly the data trace becomes invalid is shown in
Table 2 on page 10. Note that, for simplicity, data address tracing is
ignored.
Altera Corporation
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