From the datasheet :
ERASE BLOCK -> Erase All flash memory !!

Table 12. List of API

API CALL Description
PROGRAM DATA BYTE Write a byte in flash memory
PROGRAM DATA PAGE Write a page (128 bytes) in flash memory
PROGRAM EEPROM BYTE Write a byte in Eeprom memory
ERASE BLOCK Erase all flash memory
ERASE BOOT VECTOR (SBV) Erase the boot vector
PROGRAM BOOT VECTOR (SBV) Write the boot vector
PROGRAM EXTRA BYTE (EB) Write the extra byte
READ DATA BYTE
READ EEPROM BYTE
READ FAMILY CODE
READ MANUFACTURER CODE
READ PRODUCT NAME
READ REVISION NUMBER
READ STATUS BIT (BSB) Read the status bit
READ BOOT VECTOR (SBV) Read the boot vector
READ EXTRA BYTE (EB) Read the extra byte
PROGRAM X2 Write the hardware flag for X2 mode
READ X2 Read the hardware flag for X2 mode
PROGRAM BLJB Write the hardware flag BLJB
READ BLJB Read the hardware flag BLJB