ATMEGA640 datasheet(74/449 Pages) ATMEL

74 / 449 page

ATmega640/1280/1281/2560/2561

2549K–AVR–01/07

When the BOOTRST Fuse is programmed, the Boot section size set to 8K bytes and the

IVSEL bit in the MCUCR Register is set before any interrupts are enabled, the most typ-

ical and general program setup for the Reset and Interrupt Vector Addresses is:

Address

Labels

Code

Comments

;

.org 0x1F000

0x1F000

jmp

RESET

; Reset handler

0x1F002

jmp

EXT_INT0

; IRQ0 Handler

0x1F004

jmp

EXT_INT1

; IRQ1 Handler

...

;

0x1F070

jmp

USART3_TXC

; USART3 TX Complete Handler

;

0x1F072

RESET:

ldi

r16,high(RAMEND) ; Main program start

0x1F073

out

SPH,r16

; Set Stack Pointer to top of RAM

0x1F074

ldi

r16,low(RAMEND)

0x1F075

out

SPL,r16

0x1F076

sei

; Enable interrupts

0x1FO77

<instr>

xxx

Moving Interrupts

Between Application and

Boot Section

The MCU Control Register controls the placement of the Interrupt Vector table, see

Code Example below. For more details, see “Reset and Interrupt Handling” on page 17.

Assembly Code Example

Move_interrupts:

; Get MCUCR

r16, MCUCR

mov

r17, r16

; Enable change of Interrupt Vectors

ori

r16, (1<<IVCE)

out

MCUCR, r16

; Move interrupts to Boot Flash section

ori

r16, (1<<IVSEL)

out

MCUCR, r17

ret

C Code Example

void

Move_interrupts(void)

{

uchar temp;

/* Get MCUCR*/

temp = MCUCR;

/* Enable change of Interrupt Vectors */

MCUCR = temp|(1<<IVCE);

/* Move interrupts to Boot Flash section */

MCUCR = temp|(1<<IVSEL);

}

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