--- chapter.sgml.orig Fri Sep 9 20:51:48 2005
+++ chapter.sgml.4 Fri Sep 9 21:59:16 2005
@@ -117,17 +117,23 @@
null-modem cable
- A null-modem cable passes some signals, such as signal
- ground, straight through, but switches other signals. For
- example, the send data pin on one end goes to the
- receive data pin on the other end.
+ A null-modem cable passes some signals, such as Signal
+ Ground, straight-through, but switches other signals. For
+ example, the Transmitted Data pin on one end goes to the
+ Deceived Data pin on the other end.
- If you like making your own cables, you can construct
- a null-modem cable for use with
- terminals. This table shows the RS-232C signal names and the pin
- numbers on a DB-25 connector.
+ You can also construct your own null-modem cable for use with
+ terminals (e.g., for quality purposes). This table shows the RS-232C
+ signals and the pin
+ numbers on a DB-25 connector. Note that the standard also calls for a
+ straight-through pin 1 to pin 1 protective ground
+ line, but it is often omitted. Some terminals can get by using only
+ pins 2, 3 and 7, while others require different configurations than
+ the examples shown below.
-
+
+
- Connect Data Set Ready (DSR) and
- Data Carrier Detect (DCD) internally in the
- connector hood, and then to Data Terminal
- Ready (DTR) in the remote hood.
+ When one pin at one end connects to a pair of pins
+ at the other end, it is usually implemented with one short
+ wire between the pair of pins in their connector and a
+ long wire to the other single pin.
+
+ The above designs seems to be the most popular. In another
+ variation (explained in the book RS-232 Made
+ Easy) SG connects to SG, TD connects to RD, RTS and
+ CTS connect to DCD, DTR connects to DSR, and vice-versa.Standard RS-232C CablesRS-232C cables
- A standard serial cable passes all the RS-232C signals
- straight-through. That is, the send data pin on one
- end of the cable goes to the send data pin on the
+ A standard serial cable passes all of the RS-232C signals
+ straight through. That is, the Transmitted Data pin on one
+ end of the cable goes to the Transmitted Data pin on the
other end. This is the type of cable to use to connect a modem to your
FreeBSD system, and is also appropriate for some
terminals.
@@ -243,8 +444,8 @@
construct a cable, you need to make sure it will fit the ports on
your terminal and on the FreeBSD system.
- Most terminals will have DB25 ports. Personal computers,
- including PCs running FreeBSD, will have DB25 or DB9 ports. If you
+ Most terminals will have DB-25 ports. Personal computers,
+ including PCs running FreeBSD, will have DB-25 or DB-9 ports. If you
have a multiport serial card for your PC, you may have RJ-12 or
RJ-45 ports.
@@ -976,39 +1177,60 @@
cable should suffice as long as all of the normal signals
are wired:
-
-
- Transmitted Data (TD)
-
-
-
- Received Data (RD)
-
-
-
- Request to Send (RTS)
-
-
-
- Clear to Send (CTS)
-
-
-
- Data Set Ready (DSR)
-
-
-
- Data Terminal Ready (DTR)
-
-
-
- Carrier Detect (CD)
-
-
-
- Signal Ground (SG)
-
-
+
+ Signal Names
+
+
+
+
+ Acronyms
+ Names
+
+
+
+
+
+ RD
+ Received Data
+
+
+
+ TD
+ Transmitted Data
+
+
+
+ DTR
+ Data Terminal Ready
+
+
+
+ DSR
+ Data Set Ready
+
+
+
+ DCD
+ Data Carrier Detect (RS-232's Received Line
+ Signal Detector)
+
+
+
+ SG
+ Signal Ground
+
+
+
+ RTS
+ Request to Send
+
+
+
+ CTS
+ Clear to Send
+
+
+
FreeBSD needs the RTS and
CTS signals for flow-control at speeds above