 The first type is characterized by small pages and one or more internal SRAM page buffers allowing a complete page to be read to the buffer, partially modified, and then written back (for example, the Atmel AT45 "DataFlash" or the Micron Technology Page Erase NOR Flash).The second type has larger sectors.The smallest sectors typically found in an SPI flash are 4 kB, but they can be as large as 64 kB.