Datasheet

59
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
12.3 Register description
12.3.1 MCUCR – MCU Control Register
Note: 1. Only available in the Atmel ATmega169PA/329PA/3290PA/649P/6490P picoPower devices.
• 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 Loader section of the Flash. The actual
address of the start of the Boot Flash Section is determined by the BOOTSZ Fuses. Refer to the section ”Boot
Loader Support – Read-While-Write Self-Programming” on page 278 for details.
• Bit 0 – IVCE: Interrupt Vector Change Enable
The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is cleared by hardware four
cycles after it is written or when IVSEL is written. Setting the IVCE bit will disable interrupts, as explained in the
description in ”Moving interrupts between application and boot space” on page 58. See Code Example.
Bit 7 6 5 4 3 2 1 0
0x35 (0x55)
JTD BODS
(1)
BODSE
(1)
PUD – – IVSEL IVCE MCUCR
Read/Write R/W R R R/W R R R/W R/W
Initial Value 0 0 0 0 0 0 0 0