Rainbow Electronics ATtiny10 - Manual (Page 36)

36
8127B–AVR–08/09
ATtiny4/5/9/10
0x000B RESET: ldi r16, high(RAMEND); Main program start
0x000C out SPH,r16 ; Set Stack Pointer
0x000D ldi r16, low(RAMEND) ; to top of RAM
0x000E out SPL,r16
0x000F sei ; Enable interrupts
0x0010
... ...
9.2 External Interrupts
External Interrupts are triggered by the INT0 pin or any of the PCINT3..0 pins. Observe that, if
enabled, the interrupts will trigger even if the INT0 or PCINT3..0 pins are configured as outputs.
This feature provides a way of generating a software interrupt. Pin change 0 interrupts PCI0 will
trigger if any enabled PCINT3..0 pin toggles. The PCMSK Register controls which pins contrib-
ute to the pin change interrupts. Pin change interrupts on PCINT3..0 are detected
asynchronously, which means that these interrupts can be used for waking the part also from
sleep modes other than Idle mode.
The INT0 interrupt can be triggered by a falling or rising edge or a low level. This is set up as
shown in
“EICRA – External Interrupt Control Register A” on page 37 . When the INT0 interrupt is
enabled and configured as level triggered, the interrupt will trigger as long as the pin is held low.
Note that recognition of falling or rising edge interrupts on INT0 requires the presence of an I/O
clock, as described in
“Clock System” on page 17 .
9.2.1 Low Level Interrupt
A low level interrupt on INT0 is detected asynchronously. This means that the interrupt source
can be used for waking the part also from sleep modes other than Idle (the I/O clock is halted in
all sleep modes except Idle).
Note that if a level triggered interrupt is used for wake-up from Power-down, the required level
must be held long enough for the MCU to complete the wake-up to trigger the level interrupt. If
the level disappears before the end of the Start-up Time, the MCU will still wake up, but no inter-
rupt will be generated. The start-up time is defined as described in
“Clock System” on page 17 .
If the low level on the interrupt pin is removed before the device has woken up then program
execution will not be diverted to the interrupt service routine but continue from the instruction fol-
lowing the SLEEP command.
9.2.2 Pin Change Interrupt Timing
A timing example of a pin change interrupt is shown in Figure 9-1 .