74.6.5.1 Maximum QSPI Frequency

The QSPI GCLK frequency must be set to the target frequency f_QSCK. The following formulas provide the achievable QSPI frequency in Host Read and Host Write modes. When the result of these formulas exceeds the f_{QSCK_MAX} parameter provided in the tables in QSPI Timings, f_{QSCK_MAX} applies.

• Host Write in Single Data Rate Mode
  $f_{\mathrm{QSCK}}=\frac{1}{({\mathrm{QSPI}}_2+t_{\mathrm{SU\_CLIENT}})}$

  Where t_{SU_CLIENT} is the input setup time of the client device.

• Host Read in Single Data Rate Mode
  ${\mathit{\text{f}}}_{\mathrm{QSCK}}=\frac{1}{\mathit{\text{Q}}\mathit{\text{S}}\mathit{\text{P}}{\mathit{\text{I}}}_0+{\mathit{\text{t}}}_{\mathrm{VALID}}}$

  Where t_VALID is the client time response to output data after detecting a QSCK edge.

  • For a QSPI client device with t_VALID (or t_V) = 12 ns, with QSPI₀ = 1.0 ns, f_QSCK max = 77 MHz.
  • For a QSPI Flash memory device with t_VALID (or t_V) = 6 ns, and QSPI₀ = 1.0 ns, the formula returns a value of 143 MHz, therefore f_QSCK = 133 MHz applies in this case.
• Host Write in Dual Data Rate Mode
  $f_{\mathrm{QSCK}}=\frac{0.5}{({QSPI}_{12}+t_{\mathrm{SU\_CLIENT}})}$

  Where t_{SU_CLIENT} is the input setup time of the client device.

• Host Read in Dual Data Rate Mode
  $f_{\mathrm{QSCK}}=\frac{1}{\text{2x(QSP}{\text{I}}_{10}+t_{\mathrm{VALID}}\text{)}}$

  Where t_VALID is the client time response to output data after detecting a QSCK edge.

  • For a QSPI Flash memory device with t_VALID (or t_V) = 6 ns, and QSPI₁₀ = 1.0 ns, the formula returns a value of 71 MHz.