NAND Low level flash routiens

[M Sudharshana-A18475]

Hi,
	I do believe NAND flash manufacturers give low level flash
routines to erase/program data on the flash memory. While providing
them, they do mention unit of erase is of minimum 4K. Would this still
hold good with low level flash routines that some embedded device
manufacturers? Or would this erase be of the unit of sector size which
are usually of 64K/128K/256K ?

Thanks
Sudhi