ATMEGA8芯片详细中文指南

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"ATMEGA8芯片中文资料" ATMEGA8是一款由Atmel公司（现已被Microchip Technology收购）生产的微控制器，属于AVR系列。该芯片以其高性能、低功耗和丰富的内置功能在嵌入式系统设计中广泛应用。ATMEGA8是一款8位微处理器，具有8KB的闪存、512字节的EEPROM和1KB的SRAM，支持ISP（In-System Programming）和IAP（In-Application Programming），这使得程序的烧录和更新变得非常方便。 ATMEGA8拥有32个可编程I/O引脚，能够适应各种外设接口需求。它集成了多个定时器/计数器，包括一个8位定时器和两个16位定时器，可以用于PWM输出、捕获和比较功能，以及中断控制。此外，还包含了多个串行通信接口，如SPI（Serial Peripheral Interface）、TWI（Two-Wire Interface，兼容I2C协议）和USART（Universal Synchronous/Asynchronous Receiver/Transmitter），能够实现与外部设备的高速通信。在模拟部分，ATMEGA8内置了ADC（Analog-to-Digital Converter），最多可以配置8个输入通道进行模数转换，这对于处理模拟信号输入非常有用。此外，ATMEGA8还配备了比较器，可以用于检测电压阈值或触发中断事件。描述中的MC14LC5480是另一个器件，它是一个通用的PCM编解码器滤波器，适用于语音数字化和重建，以及PCM系统所需的带限和平滑处理。MC14LC5480支持μ-Law和A-Law压扩，并提供20引脚DIP、SOG和SSOP封装。这个设备能够在同步和异步应用中工作，内部包含了一个精密参考电压源。其工作流程包括：输入信号通过运算放大器，然后经过一个有源R-C滤波器消除高频噪声，之后信号被转换为差分信号进行后续处理。差分信号处理可以提高信噪比，减少噪声对信号路径的影响。 ATMEGA8芯片和MC14LC5480在电子设计中分别扮演着微控制器和音频编解码的角色，它们在嵌入式系统、智能家居、物联网设备等领域都有广泛的应用。通过理解这两个器件的工作原理和特性，开发者可以更好地设计和实现各种复杂的功能。

MC14LC5480MOTOROLA

version algorithm. All of the analog circuitry involved in the

data conversion (the voltage reference, RDAC, CDAC, and

comparator) are implemented with a differential architecture.

The receive section includes the DAC described above, a

sample and hold amplifier, a 5–pole, 3400 Hz switched ca-

pacitor low–pass filter with sinX/X correction, and a 2–pole

active smoothing filter to reduce the spectral components of

the switched capacitor filter. The output of the smoothing fil-

ter is buffered by an amplifier, which is output at the RO+ and

RO– pins. These outputs are capable of driving a 4 kΩ load

differentially or a 2 kΩ load to the V

pin. The MC14LC5480

also has a pair of power amplifiers that are connected in a

push–pull configuration. The PI pin is the inverting input to

the PO– power amplifier. The non–inverting input is internally

tied to the V

pin. This allows this amplifier to be used in an

inverting gain circuit with two external resistors. The PO+

amplifier has a gain of minus one, and is internally con-

nected to the PO– output. This complete power amplifier cir-

cuit is a differential (push–pull) amplifier with adjustable gain

that is capable of driving a 300 Ω load to +12 dBm. The

power amplifier may be powered down independently of the

rest of the chip by connecting the PI pin to V

POWER–DOWN

There are two methods of putting this device into a low

power consumption mode, which makes the device nonfunc-

tional and consumes virtually no power. PDI

is the power–

down input pin which, when taken low, powers down the

device. Another way to power the device down is to hold both

the FST and FSR pins low. When the chip is powered down,

the V

, TG, RO+, RO–, PO+, PO–, and DT outputs are high

impedance. To return the chip to the power–up state, PDI

must be high and the FST frame sync pulse must be present.

The DT output will remain in a high–impedance state for at

least two FST pulses after power–up.

MASTER CLOCK

Since this codec–filter design has a single DAC architec-

ture, the MCLK pin is used as the master clock for all analog

signal processing including analog–to–digital conversion,

digital–to–analog conversion, and for transmit and receive fil-

tering functions of this device. The clock frequency applied to

the MCLK pin may be 256 kHz, 512 kHz, 1.536 MHz,

1.544 MHz, 2.048 MHz, 2.56 MHz, or 4.096 MHz. This de-

vice has a prescaler that automatically determines the proper

divide ratio to use for the MCLK input, which achieves the re-

quired 256 kHz internal sequencing clock. The clocking re-

quirements of the MCLK input are independent of the PCM

data transfer mode (i.e., Long Frame Sync, Short Frame

Sync, IDL mode, or GCI mode).

DIGITAL I/O

The MC14LC5480 is pin selectable for Mu–Law or A–Law.

Table 1 shows the 8–bit data word format for positive and

negative zero and full scale for both companding schemes

(see Tables 3 and 4 at the end of this document for a com-

plete PCM word conversion table). Table 2 shows the series

of eight PCM words for both Mu–Law and A–Law that corre-

spond to a digital milliwatt. The digital mW is the 1 kHz cal-

ibration signal reconstructed by the DAC that defines the

absolute gain or 0 dBm0 Transmission Level Point (TLP) of

the DAC. The 0 dBm0 level for Mu–Law is 3.17 dB below the

maximum level for an unclipped tone signal. The 0 dBm0

level for A–Law is 3.14 dB below the maximum level for an

unclipped tone signal. The timing for the PCM data transfer is

independent of the companding scheme selected. Refer to

Figure 2 for a summary and comparison of the four PCM

data interface modes of this device.

Table 1. PCM Codes for Zero and Full Scale

Mu–Law A–Law

Level

Sign Bit Chord Bits Step Bits Sign Bit Chord Bits Step Bits

+ Full Scale 1 0 0 0 0 0 0 0 1 0 1 0 1 0 1 0

+ Zero 1 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1

– Zero 0 1 1 1 1 1 1 1 0 1 0 1 0 1 0 1

– Full Scale 0 0 0 0 0 0 0 0 0 0 1 0 1 0 1 0

Table 2. PCM Codes for Digital mW

Mu–Law A–Law

Phase

Sign Bit Chord Bits Step Bits Sign Bit Chord Bits Step Bits

π/8 0 0 0 1 1 1 1 0 0 0 1 1 0 1 0 0

3π/8 0 0 0 0 1 0 1 1 0 0 1 0 0 0 0 1

5π/8 0 0 0 0 1 0 1 1 0 0 1 0 0 0 0 1

7π/8 0 0 0 1 1 1 1 0 0 0 1 1 0 1 0 0

9π/8 1 0 0 1 1 1 1 0 1 0 1 1 0 1 0 0

11π/8 1 0 0 0 1 0 1 1 1 0 1 0 0 0 0 1

13π/8 1 0 0 0 1 0 1 1 1 0 1 0 0 0 0 1

15π/8 1 0 0 1 1 1 1 0 1 0 1 1 0 1 0 0

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