The SRAM is divided into sub-blocks which can be switched OFF to optimize power consumption.
By default, all sub-blocks are switched ON, but it is possible to switch them OFF (excluding the first 4 KB sub-block which remains always powered) depending on the SRAM memory size use.
This behavior can be changed by configuring the RAMPSWC bit field in the Power Configuration register (PWCFG).
The first sub-block to be switched OFF is always at the top of the SRAM block memory, and the same behavior applies for the next switched OFF sub-blocks.