Flash stores the firmware for booting and it is overwritten during programming cycle. sFlash is not overwritten during a programming cycle. sFlash stands for supervisory flash.
It is used to store manufacturer specific data.
PSoc4 BLE and PRoc BLE have 512 bytes of flash. Please see the below document for using sFlash:
I already read it. but I can't see free flash exactly. how can you certificate it???