外文文獻(xiàn)及譯文學(xué)院：電氣與控制工程學(xué)院班級：測控技術(shù)與儀器1002班姓名：學(xué)號：指導(dǎo)老師：The

single-chip

microcomputer

is

the

culmination

of

both

the

development

of

the

digital

computer

and

the

integrated

circuit

arguably

the

tow

most

significant

inventions

of

the

20th

century

.These

tow

types

of

architecture

are

found

in

single-chip

microcomputer.

Some

employ

the

split

program/data

memory

of

the

Harvard

architecture,

others

follow

the

philosophy,

widely

adapted

for

general-purpose

computers

and

microprocessors,

of

making

no

logical

distinction

between

program

and

data

memory

as

in

the

Princeton

architecture.In

general

terms

a

single-chip

microcomputer

is

characterized

by

the

incorporation

of

all

the

units

of

a

computer

into

a

single

device.

ROM

is

usually

for

the

permanent,

non-volatile

storage

of

an

applications

program

.Many

microcomputers

and

microcontrollers

are

intended

for

high-volume

applications

and

hence

the

economical

manufacture

of

the

devices

requires

that

the

contents

of

the

program

memory

be

committed

permanently

during

the

manufacture

of

chips

.

Clearly,

this

implies

a

rigorous

approach

to

ROM

code

development

since

changes

cannot

be

made

after

manufacture

.This

development

process

may

involve

emulation

using

a

sophisticated

development

system

with

a

hardware

emulation

capability

as

well

as

the

use

of

powerful

software

tools.

Some

manufacturers

provide

additional

ROM

options

by

including

in

their

range

devices

with

(or

intended

for

use

with)

user

programmable

memory.

The

simplest

of

these

is

usually

device

which

can

operate

in

a

microprocessor

mode

by

using

some

of

the

input/output

lines

as

an

address

and

data

bus

for

accessing

external

memory.

This

type

of

device

can

behave

functionally

as

the

single

chip

microcomputer

from

which

it

is

derived

albeit

with

restricted

I/O

and

a

modified

external

circuit.

The

use

of

these

ROM

less

devices

is

common

even

in

production

circuits

where

the

volume

does

not

justify

the

development

costs

of

custom

on-chip

ROM;there

can

still

be

a

significant

saving

in

I/O

and

other

chips

compared

to

a

conventional

microprocessor

based

circuit.

More

exact

replacement

for

ROM

devices

can

be

obtained

in

the

form

of

variants

with

'piggy-back'

EPROM(Erasable

programmable

ROM

)sockets

or

devices

with

EPROM

instead

of

ROM.These

devices

are

naturally

more

expensive

than

equivalent

ROM

device,

but

do

provide

complete

circuit

equivalents.

EPROM

based

devices

are

also

extremely

attractive

for

low-volume

applications

where

they

provide

the

advantages

of

a

single-chip

device,

in

terms

of

on-chip

I/O,

etc.

,with

the

convenience

of

flexible

user

programmability.The

CPU

is

much

like

that

of

any

microprocessor.

Many

applications

of

microcomputers

and

microcontrollers

involve

the

handling

of

binary-coded

decimal

(BCD)

data

(for

numerical

displays,

for

example)

,hence

it

is

common

to

find

that

the

CPU

is

well

adapted

to

handling

this

type

of

data

.It

is

also

common

to

find

good

facilities

for

testing,

setting

and

resetting

individual

bits

of

memory

or

I/O

since

many

controller

applications

involve

the

turning

on

and

off

of

single

output

lines

or

the

reading

the

single

line.

These

lines

are

readily

interfaced

to

two-state

devices

such

as

switches,

thermostats,

solid-state

relays,

valves,

motor,

etc.Parallel

input

and

output

schemes

vary

somewhat

in

different

microcomputer;

in

most

a

mechanism

is

provided

to

at

least

allow

some

flexibility

of

choosing

which

pins

are

outputs

and

which

are

inputs.

This

may

apply

to

all

or

some

of

the

ports.

Some

I/

The

DS18B20

Digital

Thermometer

provides

9

to

12-bit

(configurable)

temperature

readings

which

indicate

the

temperature

of

the

device.

Information

is

sent

to/from

the

DS18B20

over

a

1-Wire

interface,

so

that

only

one

wire

(and

ground)

needs

to

be

connected

from

a

central

microprocessor

to

a

DS18B20.

Power

for

reading,

writing,

and

performing

temperature

conversions

can

be

derived

from

the

data

line

itself

with

no

need

for

an

external

power

source.

Because

each

DS18B20

contains

a

unique

silicon

serial

number,

multiple

DS18B20s

can

exist

on

the

same

1-Wire

bus.

This

allows

for

placing

temperature

sensors

in

many

different

places.

Applications

where

this

feature

is

useful

include

HVAC

environmental

controls,

sensing

temperatures

inside

buildings,

equipment

or

machinery,

and

process

monitoring

and

control.

The

block

diagram

of

Figure

1

shows

the

major

components

of

the

DS18B20.

The

DS18B20

has

four

main

data

components:

1)

64-bit

laser

ROM,

2)

temperature

sensor,

3)

nonvolatile

temperature

alarm

triggers

TH

and

TL,

and

4)

a

configuration

register.

The

device

derives

its

power

from

the

1-Wire

communication

line

by

storing

energy

on

an

internal

capacitor

during

periods

of

time

when

the

signal

line

is

high

and

continues

to

operate

off

this

power

source

during

the

low

times

of

the

1-Wire

line

until

it

returns

high

to

replenish

the

parasite

(capacitor)

supply.

As

an

alternative,

the

DS18B20

may

also

be

powered

from

an

external

3V

-

5.5V

supply.

Communication

to

the

DS18B20

is

via

a

1-Wire

port.

With

the

1-Wire

port,

the

memory

and

control

functions

will

not

be

available

before

the

ROM

function

protocol

has

been

established.

The

master

must

first

provide

one

of

five

ROM

function

commands:

1)

Read

ROM,

2)

Match

ROM,

3)

Search

ROM,

4)

Skip

ROM,

or

5)

Alarm

Search.

These

commands

operate

on

the

64-bit

laser

ROM

portion

of

each

device

and

can

single

out

a

specific

device

if

many

are

present

on

the

1-Wire

line

as

well

as

indicate

to

the

bus

master

how

many

and

what

types

of

devices

are

present.

After

a

ROM

function

sequence

has

been

successfully

executed,

the

memory

and

control

functions

are

accessible

and

the

master

may

then

provide

any

one

of

the

six

memory

and

control

function

commands.

單片機(jī)是數(shù)字計算機(jī)的開發(fā)和集成電路20世紀(jì)可以說是拖最顯著的發(fā)明之大成體系結(jié)構(gòu)，這些纖維束類型被發(fā)現(xiàn)在單芯片微型計算機(jī)。一些采用了哈佛結(jié)構(gòu)的分割程序/數(shù)據(jù)存儲器，別人遵守的理念，廣泛適用于通用計算機(jī)和微處理器，使得程序和數(shù)據(jù)存儲器之間沒有邏輯的區(qū)別在普林斯頓體系結(jié)構(gòu)。籠統(tǒng)的單芯片微型計算機(jī)，其特征在于通過計算機(jī)的所有單位納入一個單一的設(shè)備。ROM是通常的永久性的，非應(yīng)用程序的易失性存儲器。不少微機(jī)和單片機(jī)用于大批量應(yīng)用，因此，經(jīng)濟(jì)的設(shè)備制造要求的程序存儲器的內(nèi)容是在制造期間永久性的刻錄在芯片中，這意味著嚴(yán)謹(jǐn)?shù)姆椒ǎ驗樾薷腞OM代碼不能制造之后發(fā)展。這一發(fā)展過程可能涉及仿真,使用硬件仿真功能以及強大的軟件工具使用先進(jìn)的開發(fā)系統(tǒng)。

一些制造商在其提供的設(shè)備包括的范圍（或擬使用）用戶可編程內(nèi)存.其中最簡單的通常是設(shè)備能夠運行于微處理器模式通過使用一些輸入/輸出作為地址線額外的ROM選項和數(shù)據(jù)總線訪問外部內(nèi)存.這種類型的設(shè)備可以表現(xiàn)為單芯片微型計算機(jī)盡管有限制的I/O和外部修改這些設(shè)備的電路.小內(nèi)存裝置的應(yīng)用是非常普遍的在永久性內(nèi)存的制造中;但仍然可以在我節(jié)省大量成本I/O和其它芯片相比，傳統(tǒng)的基于微處理器電路.更準(zhǔn)確的ROM設(shè)備更換，可在與'形式變種背馱式'EPROM（可擦除可編程只讀存儲器）插座或存儲器，而不是ROM器件。這些器件自然價格比同等ROM設(shè)備貴，但不提供完整的等效電路.EPROM的設(shè)備也非常有吸引力對于低容量應(yīng)用中，他們提供的單芯片器件的優(yōu)勢，在以下方面的板載I/O等，在靈活的用戶可編程帶來的便利。CPU是很象微型電子計算機(jī)和微控制器的任何微電腦.許多微電腦和微控制器涉及到二進(jìn)制編碼(十進(jìn)制處理（BCD）的數(shù)據(jù)為例）數(shù)字顯示，因而，常常可以發(fā)現(xiàn)該CPU是很適合處理這種類型的數(shù)據(jù)。對設(shè)施良好與否進(jìn)行的測試，設(shè)置和重置單個位的內(nèi)存或I/O控制器的應(yīng)用程序，也是常見的因為許多涉及打開和關(guān)閉的單輸出線或在單線.這些線很容易連接到二進(jìn)制的設(shè)備，如開關(guān)，恒溫器，固態(tài)繼電器，閥門，電機(jī)等。并行輸入和輸出的計劃有所不同，在不同的微機(jī)，在大多數(shù)設(shè)立一個機(jī)制，至少選擇讓其中一些引腳輸出，一些引腳輸如是非常靈活的。這可能適用于所有或端口.有些I/O線直接連接到適當(dāng)?shù)脑O(shè)備，例如，熒光顯示器，也可以提供足夠的電流，使接口和其他設(shè)備直接相連.一些設(shè)備允許一個I/O端口,其他組件將作為系統(tǒng)總線配置為允許片外存儲器和I/O擴(kuò)展。這個設(shè)施是潛在有用的一個產(chǎn)品系列的發(fā)展，因為連續(xù)增強可能成為太上存儲器，這是不可取的，不是建立在現(xiàn)有的軟件基礎(chǔ)上的。串行通信是指與終端設(shè)備的鏈接使用少量的通訊線.這種通訊也可利用特殊的接口連接功能芯片使幾個微型機(jī)連在一起。雙方共同異步同步通信方案要求的規(guī)則提供成幀（啟動和停止）的信息。這可以作為一個硬件設(shè)施或U（擰）藝術(shù)（通用執(zhí)行（同步）異步接收器/發(fā)送器）減輕處理器（和應(yīng)用程序）的這種低層次的確費時.它也只需要選擇一個波特率及其他可能的選擇（停止位，奇偶校驗等）和負(fù)載號碼（或讀取），串行發(fā)送器（或接收）的緩沖器.進(jìn)行適當(dāng)?shù)母袷降臄?shù)據(jù)串行處理，然后由硬件電路完成。該DS18B20數(shù)字溫度計提供9位至12位攝氏溫度測量，并與非易失性用戶可編程上下觸發(fā)點報警功能。DS18B20的通信通過一個1-Wire總線，按照定義，只需要一個數(shù)據(jù)線（和地線）與中央微處理器通信。它具有-55°C至+125°C的工作溫度范圍，精確到±0.5°C在-10°C至+85°C。此外，DS18B20可以直接從數(shù)據(jù)線（“寄生電源”）獲得電力，省去了外部電源。每個DS18B20都有一個唯一的64位序列碼，它允許多個DS18B20s到相同的1-Wire總線上運行。因此，它是簡單的使用一個微處理器來控制分布在大面積上許多DS18B20s。應(yīng)用可以受益于這個功能包括HVAC環(huán)境控制，建筑物內(nèi)部的溫度監(jiān)測系統(tǒng)，設(shè)備或機(jī)械，過程監(jiān)測和控制系統(tǒng)。該DS18B20可以通過在VDD引腳上的外部電源供電，也可以在“寄生供電”模式，它允許DS18B20來沒有本地外部電源正常工作。寄生電源是用于需要遠(yuǎn)程溫度傳感或應(yīng)用程序非常有用非常空間受限。圖1顯示了DS18B20的寄生功率控制電路，其中“偷”的力量從1-Wire總線通過DQ針時總線高。失竊的主管權(quán)力的DS18B20在總線處于高，一些電荷存儲在寄生電源電容（CPP）提供電源時，總線低。當(dāng)DS18B20采用的是寄生供電模式，VDD引腳必須連接到地面。在寄生供電模式，在1-Wire總線和CPP能夠提供足夠的電流，以DS18B20的大多數(shù)操作，只要滿足指定的時間和電壓要求（見DC電氣特性和AC電氣特性）。然而，DS18B20從暫存存儲器進(jìn)行溫度轉(zhuǎn)換或復(fù)制數(shù)據(jù)時，EEPROM時，工作電流可高達(dá)1.5毫安。該電流可能會造成整個弱1-Wire上拉電阻不可接受的電壓降，是更多的電流比可通過CPP提供。為了確保DS18B20的有足夠的電源電流，就必須提供1-Wire總線強上拉每當(dāng)溫度轉(zhuǎn)換正在發(fā)生或數(shù)據(jù)被復(fù)制暫存器到EEPROM中。這可以通過使用一個MOSFET直接拉路公交車到鐵路如圖4來完成。一個轉(zhuǎn)換T[44H]或復(fù)制暫存器[后的1-Wire總線必須切換到的10μs內(nèi)強上拉（最大）48小時]命令發(fā)出，而總線必須轉(zhuǎn)換（tCONV時間）或數(shù)據(jù)傳輸（TWR=10ms）的持續(xù)時間高舉的上拉。而拉啟用沒有其他活動可以采取的1-Wire總線上的地方。該DS18B20也可通過連接外部電源為VDD端子，如圖5的傳統(tǒng)方法提供動力。這種方法的優(yōu)點是，不需要在MOSFET上拉，并在1-Wire總線空閑時，以過程中的溫度轉(zhuǎn)換時間進(jìn)行其它流量。不建議使用寄生電源的溫度高于100°C，因為DS18B20可能無法維持通訊由于能夠在這些溫度下存在較高的漏電流。對于應(yīng)用中，這樣的溫度是可能的，強烈建議DS18B20由外部電源供電。在某些情況下，總線主機(jī)可能不知道總線上的DS18B20s是否是寄生蟲供電或由外部供應(yīng)。主需要這個信息來確定是否應(yīng)在溫度轉(zhuǎn)換中使用的強大的總線上拉。要獲得這些信息，主機(jī)可以發(fā)出跳過ROM[CCH]命令，接著讀電源[B4H]命令后面加上一個“讀時隙”。在讀時隙，寄生蟲供電DS18B20s將拉動總線低，外部供電DS18B20s會讓總線仍然很高。如果總線被拉低，主人知道它必須在溫度轉(zhuǎn)換提供強上拉的1-Wire總線上。當(dāng)你準(zhǔn)備選擇一個溫度傳感器，你不再局限于一個模擬輸出或數(shù)字輸出設(shè)備。現(xiàn)在有一個廣泛選擇的傳感器類型，其中之一應(yīng)該符合你的系統(tǒng)的需求。直到最近，市場