Please provide more details: 1. Is it on ZIF or in circuit programming? 2. What is the exact error message? 3. What means "not work every time"? 4. Did you try to use slower speed?
Yes, is it on ZIF .Not error message on writing.Error message on verifying (when compare data ).Yes,I tried use slower speed. Sorry,but I don’t speak english.
Yes,I tried to delete before write but information still remaining. I managed to write 5 pieces but I have a lot of flash written. Last ten attempts were failed.
The chip must be erased before can be correctly programmed new data. So, use the slow speed to repeat the erase untill it is erased. Change to normal speed for writting.