ATmega48 datasheet(62/340 Pages) ATMEL

62 / 340 page

7530H–AVR–02/09

ATmega48/88/168 Automotive

Note:

If Interrupt Vectors are placed in the Boot Loader section and Boot Lock bit BLB02 is programmed,

interrupts are disabled while executing from the Application section. If Interrupt Vectors are placed

in the Application section and Boot Lock bit BLB12 is programed, interrupts are disabled while

executing from the Boot Loader section. Refer to the section “Boot Loader Support –

Read-While-Write Self-Programming, ATmega88 and ATmega168” on page 263 for details on

Boot Lock bits.

This bit is not available in ATmega48.

• 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 IVSEL description above. See Code Example below.

This bit is not available in ATmega48.

10. I/O-Ports

10.1

Introduction

All AVR ports have true Read-Modify-Write functionality when used as general digital I/O ports.

This means that the direction of one port pin can be changed without unintentionally changing

the direction of any other pin with the SBI and CBI instructions. The same applies when chang-

ing drive value (if configured as output) or enabling/disabling of pull-up resistors (if configured as

input). Each output buffer has symmetrical drive characteristics with both high sink and source

capability. The pin driver is strong enough to drive LED displays directly. All port pins have indi-

vidually selectable pull-up resistors with a supply-voltage invariant resistance. All I/O pins have

protection diodes to both V

CC and Ground as indicated in Figure 10-1. Refer to “Electrical Char-

acteristics” on page 298 for a complete list of parameters.

Assembly Code Example

Move_interrupts:

; Enable change of Interrupt Vectors

ldi

r16, (1<<IVCE)

out

MCUCR, r16

; Move interrupts to Boot Flash section

ldi

r16, (1<<IVSEL)

out

MCUCR, r16

ret

C Code Example

void

Move_interrupts(void)

{

/* Enable change of Interrupt Vectors */

MCUCR = (1<<IVCE);

/* Move interrupts to Boot Flash section */

MCUCR = (1<<IVSEL);

}

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