2486MAVR12/03
Features
High-performance, Low-power AVR
8-bit Microcontroller
Advanced RISC Architecture
130 Powerful Instructions Most Single-clock Cycle Execution
32 x 8 General Purpose Working Registers
Fully Static Operation
Up to 16 MIPS Throughput at 16 MHz
On-chip 2-cycle Multiplier
Nonvolatile Program and Data Memories
8K Bytes of In-System Self-Programmable Flash
Endurance: 10,000 Write/Erase Cycles
Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
512 Bytes EEPROM
Endurance: 100,000 Write/Erase Cycles
1K Byte Internal SRAM
Programming Lock for Software Security
Peripheral Features
Two 8-bit Timer/Counters with Separate Prescaler, one Compare Mode
One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture
Mode
Real Time Counter with Separate Oscillator
Three PWM Channels
8-channel ADC in TQFP and MLF package
Six Channels 10-bit Accuracy
Two Channels 8-bit Accuracy
6-channel ADC in PDIP package
Four Channels 10-bit Accuracy
Two Channels 8-bit Accuracy
Byte-oriented Two-wire Serial Interface
Programmable Serial USART
Master/Slave SPI Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
On-chip Analog Comparator
Special Microcontroller Features
Power-on Reset and Programmable Brown-out Detection
Internal Calibrated RC Oscillator
External and Internal Interrupt Sources
Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and
Standby
I/O and Packages
23 Programmable I/O Lines
28-lead PDIP, 32-lead TQFP, and 32-pad MLF
Operating Voltages
2.7 - 5.5V (ATmega8L)
4.5 - 5.5V (ATmega8)
Speed Grades
0 - 8 MHz (ATmega8L)
0 - 16 MHz (ATmega8)
Power Consumption at 4 Mhz, 3V, 25
C
Active: 3.6 mA
Idle Mode: 1.0 mA
Power-down Mode: 0.5 A
8-bit
with 8K Bytes
In-System
Programmable
Flash
ATmega8
ATmega8L
Rev. 2486MAVR12/03
4
ATmega8(L)
2486MAVR12/03
The AVR core combines a rich instruction set with 32 general purpose working registers.
All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing
two independent registers to be accessed in one single instruction executed in one clock
cycle. The resulting architecture is more code efficient while achieving throughputs up to
ten times faster than conventional CISC microcontrollers.
The ATmega8 provides the following features: 8K bytes of In-System Programmable
Flash with Read-While-Write capabilities, 512 bytes of EEPROM, 1K byte of SRAM, 23
general purpose I/O lines, 32 general purpose working registers, three flexible
Timer/Counters with compare modes, internal and external interrupts, a serial program-
mable USART, a byte oriented Two-wire Serial Interface, a 6-channel ADC (eight
channels in TQFP and MLF packages) where four (six) channels have 10-bit accuracy
and two channels have 8-bit accuracy, a programmable Watchdog Timer with Internal
Oscillator, an SPI serial port, and five software selectable power saving modes. The Idle
mode stops the CPU while allowing the SRAM, Timer/Counters, SPI port, and interrupt
system to continue functioning. The Power-down mode saves the register contents but
freezes the Oscillator, disabling all other chip functions until the next Interrupt or Hard-
ware Reset. In Power-save mode, the asynchronous timer continues to run, allowing the
user to maintain a timer base while the rest of the device is sleeping. The ADC Noise
Reduction mode stops the CPU and all I/O modules except asynchronous timer and
ADC, to minimize switching noise during ADC conversions. In Standby mode, the crys-
tal/resonator Oscillator is running while the rest of the device is sleeping. This allows
very fast start-up combined with low-power consumption.
The device is manufactured using Atmel's high density non-volatile memory technology.
The Flash Program memory can be reprogrammed In-System through an SPI serial
interface, by a conventional non-volatile memory programmer, or by an On-chip boot
program running on the AVR core. The boot program can use any interface to download
the application program in the Application Flash memory. Software in the Boot Flash
Section will continue to run while the Application Flash Section is updated, providing
true Read-While-Write operation. By combining an 8-bit RISC CPU with In-System Self-
Programmable Flash on a monolithic chip, the Atmel ATmega8 is a powerful microcon-
troller that provides a highly-flexible and cost-effective solution to many embedded
control applications.
The ATmega8 AVR is supported with a full suite of program and system development
tools, including C compilers, macro assemblers, program debugger/simulators, In-Cir-
cuit Emulators, and evaluation kits.
Disclaimer
Typical values contained in this datasheet are based on simulations and characteriza-
tion of other AVR microcontrollers manufactured on the same process technology. Min
and Max values will be available after the device is characterized.
5
ATmega8(L)
2486MAVR12/03
Pin Descriptions
VCC
Digital supply voltage.
GND
Ground.
Port B (PB7..PB0) XTAL1/
XTAL2/TOSC1/TOSC2
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port B output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Depending on the clock selection fuse settings, PB6 can be used as input to the invert-
ing Oscillator amplifier and input to the internal clock operating circuit.
Depending on the clock selection fuse settings, PB7 can be used as output from the
inverting Oscillator amplifier.
If the Internal Calibrated RC Oscillator is used as chip clock source, PB7..6 is used as
TOSC2..1 input for the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.
The various special features of Port B are elaborated in "Alternate Functions of Port B"
on page 56 and "System Clock and Clock Options" on page 23.
Port C (PC5..PC0)
Port C is an 7-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port C output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port C pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electri-
cal characteristics of PC6 differ from those of the other pins of Port C.
If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on
this pin for longer than the minimum pulse length will generate a Reset, even if the clock
is not running. The minimum pulse length is given in Table 15 on page 36. Shorter
pulses are not guaranteed to generate a Reset.
The various special features of Port C are elaborated on page 59.
Port D (PD7..PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each
bit). The Port D output buffers have symmetrical drive characteristics with both high sink
and source capability. As inputs, Port D pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset
condition becomes active, even if the clock is not running.
Port D also serves the functions of various special features of the ATmega8 as listed on
page 61.
RESET
Reset input. A low level on this pin for longer than the minimum pulse length will gener-
ate a reset, even if the clock is not running. The minimum pulse length is given in Table
15 on page 36. Shorter pulses are not guaranteed to generate a reset.
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