SPRZ171T December   2004  – September 2020 SM320F2801-EP , SM320F2808-EP , TMS320F2801 , TMS320F2801-Q1 , TMS320F28015 , TMS320F28016 , TMS320F28016-Q1 , TMS320F2802 , TMS320F2802-Q1 , TMS320F2806 , TMS320F2806-Q1 , TMS320F2808 , TMS320F2808-Q1 , TMS320F2809 , TMS320F2809-Q1

 

  1. 1Introduction
  2. 2Device and Development Tool Support Nomenclature
  3. 3Device Markings
  4. 4Silicon Change Overview
  5. 5Usage Notes and Known Design Exceptions to Functional Specifications
    1. 5.1 Usage Notes
      1. 5.1.1 PIE: Spurious Nested Interrupt After Back-to-Back PIEACK Write and Manual CPU Interrupt Mask Clear Usage Note
    2. 5.2 Known Design Exceptions to Functional Specifications
      1.      Advisory
      2.      Advisory
      3.      Advisory
      4.      Advisory
      5.      Advisory
      6.      Advisory
      7.      Advisory
      8.      Advisory
      9.      Advisory
      10.      Advisory
      11.      Advisory
      12.      Advisory
      13.      Advisory
      14.      Advisory
      15.      Advisory
      16.      Advisory
      17.      Advisory
      18.      Advisory
      19.      Advisory
      20.      Advisory
      21.      Advisory
      22.      Advisory
  6. 6Documentation Support
  7. 7Trademarks
  8. 8Revision History

Advisory

eQEP: Missed First Index Event

Revision(s) Affected

0, A on F2809 silicon

0, A on C280x silicon

0, A, B, C on F2801, F2802, F2806, and F2808 silicon

Details

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 (that is, QEPI edge occurs before the corresponding QEPA/QEPB edge), the QEPI signal should be delayed by an amount greater than "td + 2*SYSCLKOUT".