XiP is a mode in Flash memory where one can avoid sending commands, and only
send address. Flash memory must be pre-configured to support this. The SPI
Controller must also be programmed with CMDSKIP option. Since the commands are
always sent in single line (even if Quad/Dual are chosen) the advantage can be
calculated as follows, for a case of Quad Mode with SPI Clock Freq equal to
SCLK Clock Freq. Total SPI bursts can be obtained if one looks at the Cache
Fill Counter values.
Total Core Clock Cycles with XiP = Total Core Clock Cycles without XiP - ((8 x
Total SPI Bursts x CCLK:SCLK Ratio) - 1)
Note - Even if XiP Mode is not enabled, one can still Execute-In-Place from
Flash memory. The major reason why XiP is called as mode is that, slow flash
devices has to support fast code execution and hence the user is expected to
program the best case features (in this case command skip).