ATmega16U4 datasheet(349/408 Pages) ATMEL

349 / 408 page

349

7766D–AVR–01/09

ATmega16U4/ATmega32U4

Notes:

1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.

2. “1” means unprogrammed, “0” means programmed

28.2

Fuse Bits

The ATmega16U4/ATmega32U4 has three bytes. Table 28-3 - Table 28-5 describe briefly the

functionality of all the fuses and how they are mapped into the Fuse bytes. Note that the fuses

are read as logical zero, “0”, if they are programmed.

Note:

1. See Table 8-2 on page 51 for BODLEVEL Fuse decoding.

BLB1 Mode

BLB12

BLB11

No restrictions for SPM or (E)LPM accessing the Boot

Loader section.

SPM is not allowed to write to the Boot Loader section.

SPM is not allowed to write to the Boot Loader section,

and (E)LPM executing from the Application section is not

allowed to read from the Boot Loader section. If Interrupt

Vectors are placed in the Application section, interrupts

are disabled while executing from the Boot Loader section.

(E)LPM executing from the Application section is not

allowed to read from the Boot Loader section. If Interrupt

Vectors are placed in the Application section, interrupts

are disabled while executing from the Boot Loader section.

Table 28-2.

Lock Bit Protection Modes

(1)(2) (Continued)

Memory Lock Bits

Protection Type

Table 28-3.

Extended Fuse Byte

Fuse Low Byte

Bit No

Description

Default Value

–7

–

–6

–

–5

–

–4

–

HWBE

Hardware Boot Enable

0 (programmed)

BODLEVEL2(1)

Brown-out Detector trigger level

0 (programmed)

BODLEVEL1(1)

Brown-out Detector trigger level

1 (unprogrammed)

BODLEVEL0(1)

Brown-out Detector trigger level

1 (unprogrammed)

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