58.6.1.2 Maximum QSPI Frequency

The following formulas provide the achievable QSCK frequency in Host Read and Host Write modes for Single Data Rate and Dual Data Rate modes, including external component timing parameters. When the result of these formulas exceeds the QSCK frequency listed in Table 58-19, the frequency indicated in Table 58-19 applies.

Host Write in Single Data Rate Mode
$f_{QSCK_MAX} = \frac{1}{Q S P I_{2} ({or Q S P I}_{5}_{}) + t_{SU_CLIENT}}$
Where t_{SU_CLIENT} is the input setup time of the client device.
Host Read in Single Data Rate Mode
$f_{QSCK_MAX} = \frac{1}{Q S P I_{0} ({or Q S P I}_{3}_{}) + t_{VALID}}$
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 = 1.2 ns, f_{QSCK_MAX} = 75.7 MHz.
- If CPU_CLK = 600 MHz and MCK = 200 MHz, this value is greater than the 50 MHz value listed in Table 58-19, therefore f_{QSCK_MAX} = 50 MHz.
Host Write in Dual Data Rate Mode
$f_{QSCK_MAX} = \frac{0.5}{_{}_{} {Q S P I}_{12} + t_{SU_CLIENT}}$
Where t_{SU_CLIENT} is the input setup time of the client device.
Host Read in Single Data Rate Mode
$f_{QSCK_MAX} = \frac{1}{2 x_{} (_{} {Q S P I}_{10} + t_{VALID})}$
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 = 1.2 ns, f_{QSCK_MAX} = 69 MHz.
- If CPU_CLK = 600 MHz and MCK = 200 MHz, this value is greater than the 50 MHz value listed in Table 58-19, therefore f_{QSCK_MAX} = 50 MHz.