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Advisory — eQEP: Missed First Index Event
Advisory
eQEP: Missed First Index Event
Revision(s) Affected
Details
A
If the first index event edge at the QEPI input occurs at any time from one system clock
cycle before the corresponding QEPA/QEPB edge to two system clock cycles after the
corresponding QEPA/QEP edge, then the eQEP module may miss this index event. This
can result in the following behavior:
•
QPOSCNT will not be reset on the first index event if QEPCTL[PCRM] = 00b or 10b
(position counter reset on an index event or position counter reset on the first index
event).
•
The first index event marker flag (QEPSTS[FIMF]) will not be set.
Workaround(s)
Reliable operation is achieved by delaying the index signal such that the QEPI event
edge occurs at least two system clock cycles after the corresponding QEPA/QEPB
signal edge. For cases where the encoder may impart a negative delay (td) to the QEPI
signal with respect to the corresponding QEPA/QEPB signal (i.e., QEPI edge occurs
before the corresponding QEPA/QEPB edge), the QEPI signal should be delayed by an
amount greater than "td + 2*SYSCLKOUT".
15
SPRZ272F–September 2007–Revised April 2011
TMS320F2833x and TMS320F2823x DSC Silicon Errata
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