ATMEGA8A-MUR Atmel, ATMEGA8A-MUR Datasheet - Page 67
ATMEGA8A-MUR
Manufacturer Part Number
ATMEGA8A-MUR
Description
MCU AVR 8KB FLASH 16MHZ 32QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheet
1.ATMEGA8A-MU.pdf
(308 pages)
Specifications of ATMEGA8A-MUR
Core Processor
AVR
Core Size
8-Bit
Speed
16MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
23
Program Memory Size
8KB (4K x 16)
Program Memory Type
FLASH
Eeprom Size
512 x 8
Ram Size
1K x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
*
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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13. External Interrupts
13.1
13.1.1
8159D–AVR–02/11
Register Description
MCUCR – MCU Control Register
The external interrupts are triggered by the INT0, and INT1 pins. Observe that, if enabled, the
interrupts will trigger even if the INT0:1 pins are configured as outputs. This feature provides a
way of generating a software interrupt. The external interrupts can be triggered by a falling or ris-
ing edge or a low level. This is set up as indicated in the specification for the MCU Control
Register – MCUCR. When the external interrupt is enabled and is 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 and INT1 requires the presence of an I/O clock, described in
Systems and their Distribution” on page
asynchronously. This implies that these interrupts can be used for waking the part also from
sleep modes other than Idle mode. The I/O clock is halted in all sleep modes except Idle mode.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the changed
level must be held for some time to wake up the MCU. This makes the MCU less sensitive to
noise. The changed level is sampled twice by the Watchdog Oscillator clock. The period of the
Watchdog Oscillator is 1 µs (nominal) at 5.0V and 25°C. The frequency of the Watchdog Oscilla-
tor is voltage dependent as shown in
wake up if the input has the required level during this sampling or if it is held until the end of the
start-up time. The start-up time is defined by the SUT Fuses as described in
Clock Options” on page
disappears before the end of the start-up time, the MCU will still wake up, but no interrupt will be
generated. The required level must be held long enough for the MCU to complete the wake up to
trigger the level interrupt.
The MCU Control Register contains control bits for interrupt sense control and general MCU
functions.
• Bit 3, 2 – ISC11, ISC10: Interrupt Sense Control 1 Bit 1 and Bit 0
The External Interrupt 1 is activated by the external pin INT1 if the SREG I-bit and the corre-
sponding interrupt mask in the GICR are set. The level and edges on the external INT1 pin that
activate the interrupt are defined in
detecting edges. If edge or toggle interrupt is selected, pulses that last longer than one clock
period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If
Bit
Read/Write
Initial Value
R/W
SE
7
0
SM2
R/W
24. If the level is sampled twice by the Watchdog Oscillator clock but
6
0
SM1
R/W
5
0
Table
“Electrical Characteristics” on page
24. Low level interrupts on INT0/INT1 are detected
SM0
R/W
13-1. The value on the INT1 pin is sampled before
4
0
ISC11
R/W
3
0
ISC10
R/W
2
0
ISC01
R/W
1
0
ATmega8A
244. The MCU will
“System Clock and
ISC00
R/W
0
0
MCUCR
“Clock
67
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