发现最后一块的地址处可写而不可以erase,高手分析下什么原因引起的啊?

我要erase16Mflash后面的14M,每erase 块大小为128k,共要erase bootflash后面的112块,留前面16块为bootrom区,可是erase到111块时就发生了错误,现象如下:
Debug: Erase ptr=0x50e11000. origin ,Debug: In i28f128Erase, erase OK Debug:The number is 438 Debug: Entering i28f128Write function. Debug: address=0xd60000, length=80, overwrite=0 Debug: In i28f128Write, erase OK Debug:The number is 439 Debug: Entering i28f128Write function. Debug: address=0xd60014, length=2, overwrite=1 Debug: In i28f128Write, erase OK Debug: Entering i28f128Erase function. Debug: firstblock=108, numOfBlocks=1. Debug: Erase ptr=0x50e31000. origin ,Debug: In i28f128Erase, erase OK Debug:The number is 440 Debug: Entering i28f128Write function. Debug: address=0xd80000, length=80, overwrite=0 Debug: In i28f128Write, erase OK Debug:The number is 441 Debug: Entering i28f128Write function. Debug: address=0xd80014, length=2, overwrite=1 Debug: In i28f128Write, erase OK Debug: Entering i28f128Erase function. Debug: firstblock=109, numOfBlocks=1. Debug: Erase ptr=0x50e51000. origin ,Debug: In i28f128Erase, erase OK Debug:The number is 442 Debug: Entering i28f128Write function. Debug: address=0xda0000, length=80, overwrite=0 Debug: In i28f128Write, erase OK Debug:The number is 443 Debug: Entering i28f128Write function. Debug: address=0xda0014, length=2, overwrite=1 Debug: In i28f128Write, erase OK Debug: Entering i28f128Erase function. Debug: firstblock=110, numOfBlocks=1. Debug: Erase ptr=0x50e71000. origin ,Debug: In i28f128Erase, erase OK Debug:The number is 444 Debug: Entering i28f128Write function. Debug: address=0xdc0000, length=80, overwrite=0 Debug: In i28f128Write, erase OK Debug:The number is 445 Debug: Entering i28f128Write function. Debug: address=0xdc0014, length=2, overwrite=1 Debug: In i28f128Write, erase OK Debug: Entering i28f128Erase function. Debug: firstblock=111, numOfBlocks=1. Debug: Erase ptr=0x50e91000. origin ,Debug: In i28f128Erase, erase OK Debug:The number is 446 Debug: Entering i28f128Write function. Debug: address=0xde0000, length=80, overwrite=0 Debug: In i28f128Write, erase OK
value = -1 = 0xffffffff
请高手指教,非常感谢