os/doc
3
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

Editorial review of Serial Terminology and Hardware.

Browse source 
Move signal name table into this section.
Add xml ids to the tables in this section.
More commits to come.

Sponsored by:	iXsystems
This commit is contained in:
Dru Lavigne 2014-05-07 15:22:51 +00:00
parent 038d64d23a
commit ad7752d013
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=44784
1 changed files with 118 additions and 125 deletions

243
en_US.ISO8859-1/books/handbook/serialcomms/chapter.xml
View file

@ -88,28 +88,28 @@
<para>Data Communications
Equipment<indexterm><primary>DCE</primary></indexterm>
(<acronym>DTE</acronym>) is the other endpoint in a
serial communication. Typically, it is a modem.</para>
serial communication. Typically, it is a modem or serial
terminal.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>RS-232</term>
<term><acronym>RS-232</acronym></term>
<listitem>
<para>The original standard which defined hardware serial
communications. It has since been renamed to
<acronym>TIA</acronym>-232<indexterm><primary>RS-232C
cables</primary></indexterm>.</para>
<acronym>TIA-232</acronym>.</para>
</listitem>
</varlistentry>
</variablelist>
<para>When talking about communications data rates, this section
does not use the term <quote>baud</quote>. Baud refers to the
number of electrical state transitions that may be made in a
<para>When referring to communication data rates, this section
does not use the term <firstterm>baud</firstterm>. Baud refers to the
number of electrical state transitions made in a
period of time, while <acronym>bps</acronym> is the
<emphasis>correct</emphasis> term to use.</para>
correct term to use.</para>
<para>To connect a modem or serial terminal to a &os; system, a
<para>To connect a serial terminal to a &os; system, a
serial port on the computer and the proper cable to connect to
the serial device are needed. Users who are already familiar
with serial hardware and cabling can safely skip this
@ -120,30 +120,98 @@
<para>There are several different kinds of serial cables. The
two most common types are null-modem cables and standard
RS-232 cables. The documentation for the hardware should
<acronym>RS-232</acronym> cables. The documentation for the hardware should
describe the type of cable required.</para>
<para>These two types of cables differ in how the wires are
connected to the connector. Each wire represents a signal,
with the defined signals summarized in <xref
linkend="serialcomms-signal-names"/>. A standard serial
cable passes all of the <acronym>RS-232C</acronym> signals
straight through. For example, the <quote>Transmitted Data</quote> pin on
one end of the cable goes to the <quote>Transmitted
Data</quote> pin on the other end. This is the type of
cable used to connect a modem to the &os; system, and is also
appropriate for some terminals.</para>
<para>A null-modem cable
switches the <quote>Transmitted Data</quote> pin of the
connector on one end with the <quote>Received
Data</quote> pin on the other end. The connector can be
either a <acronym>DB-25</acronym> or a
<acronym>DB-9</acronym>.</para>
<para>A null-modem cable can be constructed
using the pin connections summarized in <xref
linkend="nullmodem-db25"/>, <xref
linkend="nullmodem-db9"/>, and <xref
linkend="nullmodem-db9-25"/>. While the standard
calls for a straight-through pin 1 to pin 1
<quote>Protective Ground</quote> line, it is often
omitted. Some terminals work using only pins 2, 3, and 7,
while others require different configurations. When in doubt,
refer to the documentation for the hardware.</para>
<indexterm>
<primary>null-modem cable</primary>
</indexterm>
<para>A null-modem cable passes some signals, such as
<quote>Signal Ground</quote>, straight through, but switches
other signals. For example, the <quote>Transmitted
Data</quote> pin on one end goes to the <quote>Received
Data</quote> pin on the other end.</para>
<table frame="none" pgwide="1" xml:id="serialcomms-signal-names">
<title><acronym>RS-232C</acronym> Signal Names</title>
<para>A null-modem cable can be constructed for use with
terminals. The following table shows the RS-232C <link
linkend="serialcomms-signal-names">signal names</link> and
the pin numbers on a DB-25 connector. While the standard
calls for a straight-through pin 1 to pin 1
<emphasis>Protective Ground</emphasis> line, it is often
omitted. Some terminals work using only pins 2, 3, and 7,
while others require different configurations than the
examples shown below.</para>
<tgroup cols="2">
<thead>
<row>
<entry align="left">Acronyms</entry>
<entry align="left">Names</entry>
</row>
</thead>
<table frame="none" pgwide="1">
<tbody>
<row>
<entry><acronym>RD</acronym></entry>
<entry>Received Data</entry>
</row>
<row>
<entry><acronym>TD</acronym></entry>
<entry>Transmitted Data</entry>
</row>
<row>
<entry><acronym>DTR</acronym></entry>
<entry>Data Terminal Ready</entry>
</row>
<row>
<entry><acronym>DSR</acronym></entry>
<entry>Data Set Ready</entry>
</row>
<row>
<entry><acronym>DCD</acronym></entry>
<entry>Data Carrier Detect</entry>
</row>
<row>
<entry><acronym>SG</acronym></entry>
<entry>Signal Ground</entry>
</row>
<row>
<entry><acronym>RTS</acronym></entry>
<entry>Request to Send</entry>
</row>
<row>
<entry><acronym>CTS</acronym></entry>
<entry>Clear to Send</entry>
</row>
</tbody>
</tgroup>
</table>
<table frame="none" pgwide="1" xml:id="nullmodem-db25">
<title>DB-25 to DB-25 Null-Modem Cable</title>
<tgroup cols="5">
@ -151,7 +219,7 @@
<row>
<entry align="left">Signal</entry>
<entry align="left">Pin #</entry>
<entry/>
<entry></entry>
<entry align="left">Pin #</entry>
<entry align="left">Signal</entry>
</row>
@ -233,9 +301,7 @@
</tgroup>
</table>
<para>The next two tables show two other common schemes.</para>
<table frame="none" pgwide="1">
<table frame="none" pgwide="1" xml:id="nullmodem-db9">
<title>DB-9 to DB-9 Null-Modem Cable</title>
<tgroup cols="5">
@ -243,7 +309,7 @@
<row>
<entry align="left">Signal</entry>
<entry align="left">Pin #</entry>
<entry/>
<entry></entry>
<entry align="left">Pin #</entry>
<entry align="left">Signal</entry>
</row>
@ -325,7 +391,7 @@
</tgroup>
</table>
<table frame="none" pgwide="1">
<table frame="none" pgwide="1" xml:id="nullmodem-db9-25">
<title>DB-9 to DB-25 Null-Modem Cable</title>
<tgroup cols="5">
@ -333,7 +399,7 @@
<row>
<entry align="left">Signal</entry>
<entry align="left">Pin #</entry>
<entry/>
<entry></entry>
<entry align="left">Pin #</entry>
<entry align="left">Signal</entry>
</row>
@ -422,34 +488,17 @@
to the other single pin.</para>
</note>
<para>The above designs seem to be the most popular. In
another variation, SG connects to SG, TD connects to RD, RTS
and CTS connect to DCD, DTR connects to DSR, and
vice-versa.</para>
<indexterm><primary>RS-232C cables</primary></indexterm>
<para>A standard serial cable passes all of the RS-232C signals
straight through. The <quote>Transmitted Data</quote> pin on
one end of the cable goes to the <quote>Transmitted
Data</quote> pin on the other end. This is the type of
cable used to connect a modem to the &os; system, and is also
appropriate for some terminals.</para>
<para>Serial ports are the devices through which data is
transferred between the &os; host computer and the terminal.
This section describes the kinds of ports that exist and how
they are addressed in &os;.</para>
<para>Several kinds of serial ports exist. Before purchasing or
Several kinds of serial ports exist. Before purchasing or
constructing a cable, make sure it will fit the ports on the
terminal and on the &os; system.</para>
<para>Most terminals have DB-25 ports. Personal computers may
have DB-25 or DB-9 ports. A multiport serial card may have
RJ-12 or RJ-45 ports.</para>
<para>See the documentation that accompanied the hardware for
<para>Most terminals have <acronym>DB-25</acronym> ports. Personal computers may
have <acronym>DB-25</acronym> or <acronym>DB-9</acronym>
ports. A multiport serial card may have
<acronym>RJ-12</acronym> or <acronym>RJ-45/</acronym> ports.
See the documentation that accompanied the hardware for
specifications on the kind of port or visually verify the type
of port.</para>
@ -462,28 +511,29 @@
<para>Call-in ports are named
<filename>/dev/ttyu<replaceable>N</replaceable></filename>
where <replaceable>N</replaceable> is the port number,
starting from zero. Generally, the call-in port is used
starting from zero. If a terminal is connected to the
first serial port (<filename>COM1</filename>), use
<filename>/dev/ttyu0</filename> to refer to the terminal.
If the terminal is on the second serial port
(<filename>COM2</filename>), use
<filename>/dev/ttyu1</filename>, and so forth. Generally, the call-in port is used
for terminals. Call-in ports require that the serial line
assert the Data Carrier Detect (<acronym>DCD</acronym>)
assert the <quote>Data Carrier Detect</quote>
signal to work correctly.</para>
</listitem>
<listitem>
<para>Call-out ports are named
<filename>/dev/cuau<replaceable>N</replaceable></filename>.
<filename>/dev/cuau<replaceable>N</replaceable></filename>
on &os; versions 10.x and higher and
<filename>/dev/cuad<replaceable>N</replaceable></filename>
on &os; versions 9.x and lower.
Call-out ports are usually not used for terminals, but are
used for modems. The call-out port can be used if the
serial cable or the terminal does not support the carrier
detect signal.</para>
serial cable or the terminal does not support the <quote>Data Carrier Detect</quote>
signal.</para>
</listitem>
</itemizedlist>
<para>If a terminal is connected to the first serial port
(<filename>COM1</filename>), use
<filename>/dev/ttyu0</filename> to refer to the terminal. If
the terminal is on the second serial port
(<filename>COM2</filename>), use
<filename>/dev/ttyu1</filename>, and so forth.</para>
</sect2>
<sect2>
@ -1066,64 +1116,7 @@ ttyu5 "/usr/libexec/getty std.19200" vt100 on insecure</programlisting>
<indexterm><primary>modem</primary></indexterm>
<para>When using an external modem, a proper cable is needed. A
standard RS-232C serial cable should suffice as long as all of
the normal signals are wired:</para>
<table frame="none" pgwide="1" xml:id="serialcomms-signal-names">
<title>Signal Names</title>
<tgroup cols="2">
<thead>
<row>
<entry align="left">Acronyms</entry>
<entry align="left">Names</entry>
</row>
</thead>
<tbody>
<row>
<entry><acronym>RD</acronym></entry>
<entry>Received Data</entry>
</row>
<row>
<entry><acronym>TD</acronym></entry>
<entry>Transmitted Data</entry>
</row>
<row>
<entry><acronym>DTR</acronym></entry>
<entry>Data Terminal Ready</entry>
</row>
<row>
<entry><acronym>DSR</acronym></entry>
<entry>Data Set Ready</entry>
</row>
<row>
<entry><acronym>DCD</acronym></entry>
<entry>Data Carrier Detect (RS-232's Received Line
Signal Detector)</entry>
</row>
<row>
<entry><acronym>SG</acronym></entry>
<entry>Signal Ground</entry>
</row>
<row>
<entry><acronym>RTS</acronym></entry>
<entry>Request to Send</entry>
</row>
<row>
<entry><acronym>CTS</acronym></entry>
<entry>Clear to Send</entry>
</row>
</tbody>
</tgroup>
</table>
standard RS-232C serial cable should suffice.</para>
<para>&os; needs the <acronym>RTS</acronym> and
<acronym>CTS</acronym> signals for flow control at speeds