AT90USB646 datasheet(69/456 Pages) ATMEL

69 / 456 page

7593L–AVR–09/12

AT90USB64/128

Notes:

1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at

reset, see “Memory programming” on page 359.

2. When the IVSEL bit in MCUCR is set, Interrupt Vectors will be moved to the start of the Boot

Flash Section. The address of each Interrupt Vector will then be the address in this table

added to the start address of the Boot Flash Section.

Table 10-2 shows reset and Interrupt Vectors placement for the various combinations of

BOOTRST and IVSEL settings. If the program never enables an interrupt source, the Interrupt

Vectors are not used, and regular program code can be placed at these locations. This is also

the case if the Reset Vector is in the Application section while the Interrupt Vectors are in the

Boot section or vice versa.

Note:

1. The Boot Reset Address is shown in Table 29-8 on page 357. For the BOOTRST Fuse “1”

means unprogrammed while “0” means programmed.

10.1.1

Moving interrupts between application and boot space

The General Interrupt Control Register controls the placement of the Interrupt Vector table.

10.1.2

MCUCR – MCU Control Register

• Bit 1 – IVSEL: Interrupt Vector Select

When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the Flash

memory. When this bit is set (one), the Interrupt Vectors are moved to the beginning of the Boot

$003A

ADC

ADC Conversion Complete

$003C

EE READY

EEPROM Ready

$003E

TIMER3 CAPT

Timer/Counter3 Capture Event

$0040

TIMER3 COMPA

Timer/Counter3 Compare Match A

$0042

TIMER3 COMPB

Timer/Counter3 Compare Match B

$0044

TIMER3 COMPC

Timer/Counter3 Compare Match C

$0046

TIMER3 OVF

Timer/Counter3 Overflow

$0048

TWI

2-wire Serial Interface

$004A

SPM READY

Store Program Memory Ready

Table 10-2.

Reset and interrupt vectors placement

(1).

BOOTRST

IVSEL

Reset address

Interrupt vectors start address

0x0000

0x0002

0x0000

Boot Reset Address + 0x0002

Boot Reset Address

0x0002

Boot Reset Address

Boot Reset Address + 0x0002

Table 10-1.

Reset and interrupt vectors. (Continued)

Vector

no.

Program

address (2)

Source

Interrupt definition

Bit

JTD

–

PUD

–

IVSEL

IVCE

MCUCR

Read/write

R/W

RR/W

R/W

Initial value

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