9.4.6.9.3 GCLK Frequency Change Procedure

The GCLK frequency change procedure is as follows.

  1. Wait for QSPI_SR.RBUSY=0 and QSPI_SR.HIDLE=1.
  2. Send a QSPI_CR.LASTXFER command.
  3. Wait for QSPI_ISR.CSRA=1.
  4. Set QSPI_CR.QSPIDIS and wait for QSPI_SR.QSPIENS=0.
  5. Disable the GCLK clock.
  6. Wait for QSPI_SR.CALBSY=0.
  7. Change GCLK frequency.
  8. Write:
    • QSPI_CR.STPCAL
  9. Wait for:
    • QSPI_SR.CALBSY=0
  10. Write QSPI_CR.QSPIEN.
  11. Wait for QSPI_SR.QSPIENS=1.
  12. If automatic refresh is enabled, wait for QSPI_ISR.RFRSHD=1 by polling or interrupt (see Automatic Refresh).