Datasheet

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

30 $003A ADC ADC Conversion Complete

31 $003C EE READY EEPROM Ready

32 $003E TIMER3 CAPT Timer/Counter3 Capture Event

33 $0040 TIMER3 COMPA Timer/Counter3 Compare Match A

34 $0042 TIMER3 COMPB Timer/Counter3 Compare Match B

35 $0044 TIMER3 COMPC Timer/Counter3 Compare Match C

36 $0046 TIMER3 OVF Timer/Counter3 Overflow

37 $0048 TWI 2-wire Serial Interface

38 $004A SPM READY Store Program Memory Ready

Table 10-2. Reset and interrupt vectors placement

(1)

BOOTRST IVSEL Reset address Interrupt vectors start address

1 0 0x0000 0x0002

1 1 0x0000 Boot Reset Address + 0x0002

0 0 Boot Reset Address 0x0002

0 1 Boot Reset Address Boot Reset Address + 0x0002

Table 10-1. Reset and interrupt vectors. (Continued)

Vector

no.

Program

address

(2)

Source Interrupt definition

Bit 76543210

JTD – – PUD – – IVSEL IVCE MCUCR

Read/writeR/WRRR/WRRR/WR/W

Initial value00000000