📄 interfacing the serial - 1.htm
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>2.<o:p></o:p></span></p>
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<p><span lang=EN-US>You don't need as many wires than parallel transmission</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>串行所用导线少</span><span lang=EN-US>. If your device needs to be mounted
a far distance away from the computer then 3 core cable</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>三芯线</span><span lang=EN-US> (Null Modem Configuration) is going to
be a lot cheaper</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>经济的多</span><span lang=EN-US> that
running 19 or 25 core cable. However you must take into account</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>考虑</span><span lang=EN-US> the cost of the interfacing at each end</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>费用</span><span lang=EN-US>. </span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>3.<o:p></o:p></span></p>
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<p><span lang=EN-US>Infrared</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>红外线</span><span lang=EN-US> devices have
proven quite popular recently. You may have seen many electronic diaries
and palmtop computers </span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>笔记本电脑和掌上电脑</span><span lang=EN-US>which
have infrared capabilities build in. However could you imagine transmitting
8 bits of data at the one time across the room and being able to (from the
devices point of view</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>从设备的角度</span><span lang=EN-US>) decipher</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>译码</span><span lang=EN-US> which bits are which? Therefore serial
transmission is used where one bit is sent at a time. IrDA-1 (The first
infrared specifications</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>规范</span><span lang=EN-US>) was capable
of</span><span style='font-family:宋体;mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial'>可以</span><span lang=EN-US>115.2k baud</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>波特</span><span lang=EN-US> and was interfaced into a UART. The pulse
length however was cut down to</span><span style='font-family:宋体;
mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>脉冲宽度减小</span><span
lang=EN-US> 3/16th of a RS232 bit length to conserve power</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>节约能量</span><span lang=EN-US> considering these devices are mainly
used on</span><span style='font-family:宋体;mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial'>考虑到这些设备主要用在</span><span lang=EN-US> diaries,
laptops</span><span style='font-family:宋体;mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial'>膝上型电脑</span><span lang=EN-US> and palmtops. </span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>4.<o:p></o:p></span></p>
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<p><span lang=EN-US>Microcontroller's have also proven to be quite popular
recently</span><span style='font-family:宋体;mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial'>微处理器</span><span lang=EN-US>. Many of these
have in built SCI (Serial Communications Interfaces</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>串行通讯接口</span><span lang=EN-US>) which can be used to talk to the
outside world. Serial Communication reduces the pin count of these MPU's.
Only two pins are commonly used</span><span style='font-family:宋体;
mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>只用两个引脚</span><span
lang=EN-US>, Transmit Data (TXD) and Receive Data (RXD) compared with</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
Arial'>相比较</span><span lang=EN-US> at least 8 pins if you use a 8 bit
Parallel method (You may also require a Strobe). </span></p>
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<p class=MsoNormal align=center style='text-align:center'><i><span
lang=EN-US style='font-size:18.0pt;font-family:Arial'>Table of Contents<a
name=TOC></a><o:p></o:p></span></i></p>
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style='font-family:Arial'>
<hr size=2 width="100%" align=center>
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<p class=MsoNormal align=center style='text-align:center'><b><span
lang=EN-US style='font-size:13.5pt;font-family:Arial'>Part 1 : Hardware
(PC's)</span></b><span lang=EN-US style='font-family:Arial'><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#1">Hardware Properties</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#2">Serial Pinouts (D25
and D9 connectors)<br>
</a><a href="http://www.beyondlogic.org/serial/serial.htm#3">Pin Functions </a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#4">Null Modems </a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#5">Loopback Plugs</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#6">DTE/DCE Speeds</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#7">Flow Control </a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#8">The UART (8250's and
Compatibles) </a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#9">Type of UARTS (For
PC's) </a><br>
</span><b><span lang=EN-US style='font-size:13.5pt;font-family:Arial'>Part 2
: Serial Ports' Registers (PC's)</span></b><span lang=EN-US style='font-family:
Arial'><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#12">Port Addresses and
IRQ's</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#13">Table of Registers</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#14">DLAB ? </a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#15">Interrupt Enable
Register (IER)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#16">Interrupt
Identification Register (IIR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#17">First In / First
Out Control Register (FCR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#18">Line Control
Register (LCR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#19">Modem Control
Register (MCR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#20">Line Status
Register (LSR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#21">Modem Status
Register (MSR)</a><br>
<a href="http://www.beyondlogic.org/serial/serial.htm#22">Scratch Register</a><a
name=part1></a><o:p></o:p></span></p>
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<p class=MsoNormal><i><span lang=EN-US style='font-size:18.0pt;font-family:
Arial'>Part One : Hardware (PC's)</span></i><span lang=EN-US
style='font-family:Arial'> <o:p></o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span lang=EN-US
style='font-family:Arial'>
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<p style='margin-left:36.0pt'><a name=1><span lang=EN-US style='font-size:
13.5pt'>Hardware Properties</span><span lang=EN-US> </span></a></p>
<span style='mso-bookmark:1'></span>
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</span></span></div>
<span style='mso-bookmark:1'></span>
<p style='margin-left:36.0pt'><span lang=EN-US>Devices which use serial
cables for their communication are split into two categories</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>分为两大类</span><span
lang=EN-US>. These are DCE (Data Communications Equipment</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>通信设备</span><span
lang=EN-US>) and DTE (Data Terminal Equipment</span><span style='font-family:
宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>终端设备</span><span
lang=EN-US>.) Data Communications Equipment are devices such as your modem</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>调制解调器</span><span
lang=EN-US>, TA adapter</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>适配器</span><span lang=EN-US>, plotter etc
while Data Terminal Equipment is your Computer or Terminal</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>电脑终端</span><span
lang=EN-US>. </span></p>
<p style='margin-left:36.0pt'><span lang=EN-US>The electrical specifications
of the serial port is contained in the EIA (Electronics Industry Association)
RS232C standard</span><span style='font-family:宋体;mso-ascii-font-family:Arial;
mso-hansi-font-family:Arial'>串口电气规范</span><span lang=EN-US>. It states many
parameters such as</span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>规定了很多参数</span><span lang=EN-US> - </span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>1.<o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>A
"Space" (logic 0) will be between +3 and +25 Volts</span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'> 逻辑</span><span lang=EN-US style='font-family:Arial'>0</span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>应在</span><span lang=EN-US style='font-family:Arial'>+3 </span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>到</span><span lang=EN-US style='font-family:Arial'> +25</span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>伏之间</span><span lang=EN-US style='font-family:Arial'>. <o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>2.<o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>A
"Mark" (Logic 1) will be between -3 and -25 Volts</span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'> 逻辑</span><span lang=EN-US style='font-family:Arial'>1</span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>应在</span><span lang=EN-US style='font-family:Arial'>-3 </span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>到</span><span style='font-family:Arial'> <span lang=EN-US>-25</span></span><span
style='mso-ascii-font-family:Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:
Arial'>伏之间</span><span lang=EN-US style='font-family:Arial'>. <o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>3.<o:p></o:p></span></p>
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<p class=MsoNormal><span lang=EN-US style='font-family:Arial'>The region
between +3 and -3 volts is undefined</span><span style='mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'> </span><span
lang=EN-US style='font-family:Arial'>+3</span><span style='mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>到</span><span
lang=EN-US style='font-family:Arial'>-3</span><span style='mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>伏之间没有定义</span><span
lang=EN-US style='font-family:Arial'>. <o:p></o:p></span></p>
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