An example is shown in Figure 5. Figure 5. DDR QUAD SPI transfer One could ask ... First of all, eSPI introduces a new signal “alert”, which works like an interrupt request from Slave to the Master.

In the Single SPI mode, data is simultaneously transmitted and received, while in DUAL, QUAD and OCTAL SPI modes, data is shifted in or out respectively on two, four and eight data lines at once.