两学一做笔记本怎么写:求助:单片机如何写FLASH啊??

我用得FLASH是SST39VF040,怎么写也写不进去,读出来得还是0FF,
程序如下,
mov dptr,#5555h
mov a,#0aah
movx @dptr,a

mov dptr,#2Aaah
mov a,#55h
movx @dptr,a

mov dptr,#5555h
mov a,#80h
movx @dptr,a

mov dptr,#5555h
mov a,#0AAh
movx @dptr,a

mov dptr,#2Aaah
mov a,#55h
movx @dptr,a

clr p1.2
clr p1.3
clr p1.4 ;FLASH的高三位地址
mov dptr,#0h
mov a,#30h
movx @dptr,a
mov r0,#0
ycg:
mov r1,#0
djnz r1,$
djnz r0,ycg ;延时,等待片擦除

mov r0,#100
loop:
mov dptr,#5555h
mov a,#0aah
movx @dptr,a

mov dptr,#2Aaah
mov a,#55h
movx @dptr,a

mov dptr,#5555h
mov a,#0a0h
movx @dptr,a

mov a,#55h
mov dpl,r0
mov dph,#0
movx @dptr,a

wait1:
movx a,@dptr
cjne a,#55h,wait1 ;判断是否写进去
djnz r0,loop
end