ATTINY22L(2000) View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATTINY22L
(Rev.:2000)

8-bit Microcontroller with 2K Bytes of In-System Programmable Flash

Atmel Corporation 

Reset and Interrupt Handling

The ATtiny22L provides two interrupt sources. These interrupts and the separate reset vector, each have a separate

program vector in the program memory space. Both interrupts are assigned individual enable bits which must be set (one)

together with the I-bit in the status register in order to enable the interrupt.

The lowest addresses in the program memory space are automatically defined as the Reset and Interrupt vectors. The

complete list of vectors is shown in Table 2 . The list also determines the priority levels of the interrupts. The lower the

address the higher is the priority level. RESET has the highest priority, next is INT0 - the External Interrupt Request 0, etc.

Table 2. Reset and Interrupt Vectors

Vector No.

Program Address

Source

Interrupt Definition

1

$000

RESET

Hardware Pin, Power-on Reset and Watchdog Reset

2

$001

INT0

External Interrupt Request 0

3

$002

TIMER0, OVF0 Timer/Counter0 Overflow

The most typical program setup for the Reset and Interrupt Vector Addresses are:

Address

$000

$001

$002

$003

…

Labels

MAIN:

…

Code

rjmp RESET

rjmp EXT_INT0

rjmp TIM_OVF0

ldi r16, low(RAMEND)

out SPL, r16

<instr> xxx

…

Comments

; Reset Handler

; IRQ0 Handler

; Timer0 Overflow Handler;

; Main program start

…

Reset Sources

The ATtiny22L provides three sources of reset:

• Power-On Reset. The MCU is reset when the supply voltage is below the power-on reset threshold (VPOT).

• External Reset. The MCU is reset when a low level is present on the RESET pin for more than 50 ns.

• Watchdog Reset. The MCU is reset when the Watchdog timer period expires and the Watchdog is enabled.

During reset, all I/O registers are set to their initial values, and the program starts execution from address $000. The

instruction placed in address $000 must be an RJMP - relative jump - instruction to the reset handling routine. If the

program never enables an interrupt source, the interrupt vectors are not used, and regular program code can be placed at

these locations. The circuit diagram in Figure 21 shows the reset logic. Table 3 defines the timing and electrical parameters

of the reset circuitry.

18

ATtiny22L

Share Link: