14.5 Automatic I/O calibration is not functional

Automatic I/O calibration does not work properly and returns incorrect calibration values. As a consequence, the output impedance value is not reliable.

Work Around

Automatic I/O calibration has to be bypassed and the calibration values must be forced manually.

Configure the controller as follows:
  1. Ensure no I/O calibration sequence is started manually (SDMMC_CALCR.EN = 0).
  2. Disable automatic I/O calibration when the tuning procedure starts (SDMMC_CALCR.TUNDIS = 1).
  3. Switch off Calibration Analog Always On (SDMMC_CALCR.ALWYSON = 0).
  4. Enable calibration bypass (SDMMC_CALCR.BPEN = 1).
  5. Define the calibration P-channel and N-channel bypass values:

    • SDMMC_CALCR.CALPBP = 0x9 when VDDSDMMCx is 1.8V, or

      SDMMC_CALCR.CALPBP = 0xD when VDDSDMMCx is 3.3V

    • SDMMC_CALCR.CALNBP = 0x4 when VDDSDMMCx is 1.8V, or

      SDMMC_CALCR.CALNBP = 0x2 when VDDSDMMCx is 3.3V

Affected Device Revisions

A0

A0-D1G

A0-D2G

A1

A1-D5M

A1-D1G

A1-D2G

A1-D4G

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