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.
AVR 内核具有丰富的指令集和 32 个通用工作寄存器。所有的寄存器都直接与算逻单元
(ALU) 相连接，使得一条指令可以在一个时钟周期内同时访问两个独立的寄存器。这种结
构大大提高了代码效率，并且具有比普通的 CISC 微控制器最高至 10 倍的数据吞吐率。
ATmega8 有如下特点 :8K 字节的系统内可编程 Flash( 具有同时读写的能力，即 RWW)，
512 字节 EEPROM，1K 字节 SRAM，32 个通用 I/O 口线，32 个通用工作寄存器，三个
具有比较模式的灵活的定时器 / 计数器 (T/C), 片内 / 外中断，可编程串行 USART，面向
字节的两线串行接口， 10 位 6 路 (8 路为 TQFP 与 MLF 封装 )ADC，具有片内振荡器的
可编程看门狗定时器，一个 SPI 串行端口，以及五种可以通过软件进行选择的省电模式。
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