I have a simple doubt. There are two flash areas in this AT89C5131 chip. FM0 - user flash zone and FM1 - bootloader flash. The interrupt vector addresses for the chip begin at 0x0000. When in the bootloader(FM1), and trying to program the FM0 using the APIs provided there is no guarantee of the content in memory locations starting at 0x0000 (IVT). So there is no point in having EA enabled. My doubt is whever I come across bootloader programming it has been adviced that I diable the interrupt just for the time calling the API and then enable it. (See this http://www.keil.com/forum/docs/thread3481.asp)Should it not be that once in bootloader I diable all the interrupts (as I am not sure of the contents at 0x0000 onwards). Then I get the USB packets from the host in the bootloader only by polling and NOT by interrupt routines. Am I correct? Please advice.