ATMEGA64A-MNR Atmel, ATMEGA64A-MNR Datasheet - Page 15
ATMEGA64A-MNR
Manufacturer Part Number
ATMEGA64A-MNR
Description
IC MCU AVR 64K FLASH 8QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheet
1.ATMEGA64A-AU.pdf
(392 pages)
Specifications of ATMEGA64A-MNR
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
53
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
4K 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
*
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
2 KB
Interface Type
SPI, UART, I2C
Maximum Clock Frequency
16 MHz
Number Of Programmable I/os
53
Operating Supply Voltage
2.7 V to 5.5 V
Maximum Operating Temperature
+ 105 C
Mounting Style
SMD/SMT
Operating Temperature Range
- 40 C to + 85 C
Processor To Be Evaluated
ATMEGA64A
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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- Download datasheet (8Mb)
8160C–AVR–07/09
BOOTRST Fuse, see
281.
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are dis-
abled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled
interrupts can then interrupt the current interrupt routine. The I-bit is automatically set when a
Return from Interrupt instruction – RETI – is executed.
There are basically two types of interrupts. The first type is triggered by an event that sets the
interrupt flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vector
in order to execute the interrupt handling routine, and hardware clears the corresponding inter-
rupt flag. Interrupt flags can also be cleared by writing a logic one to the flag bit position(s) to be
cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is cleared,
the interrupt flag will be set and remembered until the interrupt is enabled, or the flag is cleared
by software. Similarly, if one or more interrupt conditions occur while the Global Interrupt Enable
bit is cleared, the corresponding interrupt flag(s) will be set and remembered until the Global
Interrupt Enable bit is set, and will then be executed by order of priority.
The second type of interrupts will trigger as long as the interrupt condition is present. These
interrupts do not necessarily have interrupt flags. If the interrupt condition disappears before the
interrupt is enabled, the interrupt will not be triggered.
When the AVR exits from an interrupt, it will always return to the main program and execute one
more instruction before any pending interrupt is served.
Note that the Status Register is not automatically stored when entering an interrupt routine, nor
restored when returning from an interrupt routine. This must be handled by software.
When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled.
No interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the
CLI instruction. The following example shows how this can be used to avoid interrupts during the
timed EEPROM write sequence.
Assembly Code Example
C Code Example
in r16, SREG
cli
sbi EECR, EEMWE
sbi EECR, EEWE
out SREG, r16
char cSREG;
cSREG = SREG;
/* disable interrupts during timed sequence */
_CLI();
EECR |= (1<<EEMWE); /* start EEPROM write */
EECR |= (1<<EEWE);
SREG = cSREG; /* restore SREG value (I-bit) */
; disable interrupts during timed sequence
/* store SREG value */
“Boot Loader Support – Read-While-Write Self-programming” on page
; store SREG value
; start EEPROM write
; restore SREG value (I-bit)
ATmega64A
15
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