66.15.1 Maximum SPI Frequency

The following formulas give maximum SPI frequency in Host Read and Write modes and in Client Read and Write modes.

• Host Write Mode

  The SPI sends data to a client device only, e.g. an LCD. The limit is given by SPI₂ (or SPI₅) timing.

• Host Read Mode

  $f_{\mathrm{SPCK}}\max =\frac{1}{{\mathrm{SPI}}_0\left(\text{or }{\mathrm{SPI}}_3\right)+t_{\mathrm{VALID}}}$

t_VALID is the client time response to output data after deleting an SPCK edge.

  The f_SPCK max is given between the maximum frequency given by the above formula and the pad I/O limitation.

• Client Read Mode

  In Client mode, SPCK is the input clock for the SPI. The max SPCK frequency is given by setup and hold timings SPI₇/SPI₈ (or SPI₁₀/SPI₁₁). Since this gives a frequency well above the pad limit, the limit in Client Read mode is given by the SPCK pad.

• Client Write Mode

  $f_{\mathrm{SPCK}}\max =\frac{1}{{\mathrm{2x(SPI}}_{\mathrm{6max}}\left(\text{or }{\mathrm{SPI}}_{\mathrm{9max}}\right)+t_{\mathrm{SETUP}}}$

t_SETUP is the setup time from the host before sampling data (6 ns).

  The f_SPCK max is given between the maximum frequency given by the above formula and the pad I/O limitation.