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AT90USB646 Datasheet(PDF) 355 Page - ATMEL Corporation |
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AT90USB646 Datasheet(HTML) 355 Page - ATMEL Corporation |
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355 / 434 page ![]() 355 7593A–AVR–02/06 AT90USB64/128 Figure 28-2. Memory Sections Note: 1. The parameters in the figure above are given in Table 28-8 on page 366. 28.4 Boot Loader Lock Bits If no Boot Loader capability is needed, the entire Flash is available for application code. The Boot Loader has two separate sets of Boot Lock bits which can be set independently. This gives the user a unique flexibility to select different levels of protection. The user can select: • To protect the entire Flash from a software update by the MCU. • To protect only the Boot Loader Flash section from a software update by the MCU. • To protect only the Application Flash section from a software update by the MCU. • Allow software update in the entire Flash. See Table 28-2 and Table 28-3 for further details. The Boot Lock bits can be set by software and in Serial or in Parallel Programming mode. They can only be cleared by a Chip Erase command only. The general Write Lock (Lock Bit mode 2) does not control the programming of the Flash memory by SPM instruction. Similarly, the general Read/Write Lock (Lock Bit mode 1) does not control reading nor writing by (E)LPM/SPM, if it is attempted. 0x0000 Flashend Program Memory BOOTSZ = '11' Application Flash Section Boot Loader Flash Section Flashend Program Memory BOOTSZ = '10' 0x0000 Program Memory BOOTSZ = '01' Program Memory BOOTSZ = '00' Application Flash Section Boot Loader Flash Section 0x0000 Flashend Application Flash Section Flashend End RWW Start NRWW Application Flash Section Boot Loader Flash Section Boot Loader Flash Section End RWW Start NRWW End RWW Start NRWW 0x0000 End RWW, End Application Start NRWW, Start Boot Loader Application Flash Section Application Flash Section Application Flash Section End Application Start Boot Loader End Application Start Boot Loader End Application Start Boot Loader |
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