ATMEGA323-8PC Atmel, ATMEGA323-8PC Datasheet - Page 32

• Manufacturer Part Number: ATMEGA323-8PC
• Description: IC AVR MCU 32K 8MHZ COM 40DIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA323-8PC

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: ATMEGA3238PC

Voltage Reference Enable
Signals and Start-up Time
Interrupt Handling
Interrupt Response Time
32
ATmega323(L)
The voltage reference has a start-up time that may influence the way it should be used.
The maximum start-up time is TBD. To save power, the reference is not always turned
on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODEN Fuse).
2. When the bandgap reference is connected to the Analog Comparator (by setting
3. When the ADC is enabled.
Thus, when the BOD is not enabled, after setting the ACBG bit, the user must always
allow the reference to start up before the output from the Analog Comparator is used.
The bandgap reference uses typically 10 µA, and to reduce power consumption in
Power-down mode, the user can avoid the three conditions above to ensure that the ref-
erence is turned off before entering Power-down mode.
The ATmega323 has two 8-bit Interrupt Mask Control Registers: GICR
rupt Control Register and TIMSK – Timer/Counter Interrupt Mask Register.
When an interrupt occurs, the Global Interrupt Enable I-bit is cleared (zero) and all inter-
rupts are disabled. The user software can set (one) the I-bit to enable nested interrupts.
The I-bit is set (one) when a Return from Interrupt instruction – RETI – is executed.
When the Program Counter is vectored to the actual Interrupt Vector in order to execute
the interrupt handling routine, hardware clears the corresponding flag that generated the
interrupt. Some of the 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
(zero), the Interrupt Flag will be set and remembered until the interrupt is enabled, or the
flag is cleared by software.
If one or more interrupt conditions occur while the Global Interrupt Enable bit is cleared
(zero), the corresponding Interrupt Flag(s) will be set and remembered until the Global
Interrupt Enable bit is set (one), and will be executed by order of priority.
Note that external level interrupt does not have a flag, and will only be remembered for
as long as the interrupt condition is present.
Note that the Status Register is not automatically stored when entering an interrupt rou-
tine and restored when returning from an interrupt routine. This must be handled by
software.
The interrupt execution response for all the enabled AVR interrupts is four clock cycles
minimum. After four clock cycles the Program Vector address for the actual interrupt
handling routine is executed. During this four clock cycle period, the Program Counter
(14 bits) is pushed onto the Stack. The vector is normally a jump to the interrupt routine,
and this jump takes three clock cycles. If an interrupt occurs during execution of a multi-
cycle instruction, this instruction is completed before the interrupt is served. If an inter-
rupt occurs when the MCU is in sleep mode, the interrupt execution response time is
increased by four clock cycles.
A return from an interrupt handling routine takes four clock cycles. During these four
clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack
Pointer is incremented by two, and the I-flag in SREG is set. When AVR exits from an
interrupt, it will always return to the main program and execute one more instruction
before any pending interrupt is served.
the ACBG bit in ACSR).
–
General Inter-
1457G–AVR–09/03