Read Operation - 3.2 English

PG153 AXI Quad SPI Product Guide

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3.2 English

In SCK ratio = 2 scenarios, a successful read operation occurs when the SPI data, launched on the falling-edge of SCK, is captured on the second rising-edge of ext_spi_clk. This means that the data should be available and stable at the time the capture happens on the second rising edge.

The worst case scenario occurs when:

   SCK has max delay on the line (that is, Max delay of STARTUP)

   SPI drives the data with max Tco 

Fmax4 = fn {STARTUP delay max, Tco-max, board routing}

Thus the actual Fmax is the one that is most restrictive amongst Fmax2, Fmax3 and Fmax4.