36.4.1.2 Single Data Rate (SDR) Speeds

In SDR mode, the data transaction occurs only on the rising edge of the clock, whereas in DDR mode the transactions occur on both the rising and falling edge of the clock, providing double the throughput. Some Serial Flash devices support commands specifically aimed at DDR mode (i.e., the 4DDRQIOR command to read from Flash using quad I/O in DDR mode in case of Spansion memories supporting DDR mode).

The following figures show the high-speed read quad lane sequence in SDR mode and DDR mode, respectively.