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Topic: NULL modem

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In the News (Tue 23 Apr 19)

  RS232 serial null modem cable wiring and tutorial
The terminology null modem for the situation where two computers communicate directly is so often used nowadays, that most people don't realize anymore the origin of the phrase and that a null modem connection is an exception, not the rule.
This means that the null modem cable allows communication as long as no flow control is needed, but when data speeds reach the limit the receivers can handle, communication may stop immediately without an assignable reason.
The simple null modem cable and the null modem cable with loop back handshaking are useful, but have no provisions for hardware flow control.
www.lammertbies.nl /comm/info/RS-232_null_modem.html   (2185 words)

  Null modem -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-17)
With a null modem connection the (additional info and facts about transmit) transmit and (additional info and facts about receive) receive lines are crosslinked.
Null modems are commonly used for file transfer between computers, or remote operation.
A null modem cable is a RS-232 serial cable where the transmit and receive lines are crosslinked.
www.absoluteastronomy.com /encyclopedia/n/nu/null_modem.htm   (361 words)

 install manual
On a serial modem cable, the pins in the connectors are wired "straight through." This means that the pins function identically on the two connectors at either end of the cable.
Null modem cables are another type of serial cable used to connect printers, terminals, and other devices.
Null modem cable wires are connected to the pins in the connectors differently from how they are attached in a modem cable.
docs.sun.com /source/800-6313-10/install.appendixe.html   (1454 words)

 Null Modem Cable   (Site not responding. Last check: 2007-10-17)
There is more than one null modem config used.
Obviously at its simplest there is a difference between a 9 pin null modem cable and a 25 pin null modem cable.
Even with just one physical connector, the simplest null modem cable just reverses the Rxd and Txd connections and normally has one or two ground connections, pins 1 and 7 in the 25 pin connector, wired straight thru.
www.vision.net.au /~timotsc/null/nullmodem.htm   (1693 words)

 Null Modem
A null modem is a specially designed cable that allows a user to connect two computers directly to each other via their communications ports (RS-232 ports).
A null modem cable was used in the past to connect two DTE (Data Terminal Equipment) devices.
The null modem is a way for those of us that missed the time of do-it-yourself computer hobby kits and garage-based startups to relive the excitement of those golden days of discovery and innovation.
www.broadbandinfo.com /internet-connections-101/hardware-and-wireless/cable-modem/null.html   (458 words)

 Serial Communication over Short Distances -- Null Modem
If two computers are within a short distance of each other, it is possible to use either a null modem cable or null modem adapter to connect the computers for serial communication.
The null modem cable for IBM computers and compatibles changes the connection of pins so that pin numbers are not connected directly to the corresponding pin numbers at the other end of the cable.
The alternative to the null modem cable is the use of a null modem adapter that changes the connection between pins and allows the use of straight through cables.
support.microsoft.com /kb/60040   (546 words)

 Byonics - TinyTrak Null Modem Gender Changers   (Site not responding. Last check: 2007-10-17)
A female to female gender changer and a null modem adapter is needed to connect a TinyTrak3 to a computer serial port.
A male to male gender changer and a null modem adapter is needed to connect a TinyTrak or TinyTrakII to a GPS.
This adapter is both a male to male gender changer, and a null modem adapter.
www.byonics.com /tinytrak/gender.php   (197 words)

 null modem @ Cablemax.com
6ft Null Modem Cable DB9 female to DB9 female, 7 conductors, shielded, molded...
6ft Null Modem Cable DB25 female to DB25 female, 8 conductors, shielded, molded...
Changes a standard data cable into a Null Modem cable...
www.cablemax.com /null-modem-data-cables.cfm   (72 words)

 What is null modem? - a definition from Whatis.com
Since a modem or DCE is not really needed to interconnect your PC with another local serial device, the DTE interface can be used by both your PC and the attached serial device.
What a null modem cable does is to make the other end of the PC or device's DTE interface look like a DCE interface.
A null modem cable is sometimes called a crossover cable.
searchnetworking.techtarget.com /sDefinition/0,,sid7_gci212677,00.html   (486 words)

 NULL Modem Cable
This 6 feet standard null modem cross cable allows downloading to many of our boards.
Please note that this is a cross cable that crosses pins 7 and 8 on both sides.
There is also a null modem cable standard that does not cross pins 7 and 8 and hence is not suitable for use with our boards.
www.bipom.com /nullmodem.shtm   (58 words)

 RS232 Serial Cable Pinouts
A Null Modem cable or Null Modem adapter simply crosses the receive and transmit lines so that transmit on one end is connected to receive on the other end and vice versa.
A Null Modem adapter is a small device that plugs in the line of a standard serial cable that converts the connection to a Null Modem connection.
Null Modem adapters are available at most computer and office supply stores for under $5.
www.taltech.com /support/pins.html   (368 words)

 RS232 serial cable pinout information
Although this serial interface is differential (the receive and transmit have their own floating ground level which is not the case with regular RS232) it is possible to connect RS232 compatible devices with this interface because the voltage levels of the bit streams are in the same range.
This input is used by modems to signal an incoming call to the attached computer.
RS232 null modem cables with handshaking can be defined in numerous ways, with loopback handshaking to each PC, or complete handshaking between the two systems.
www.lammertbies.nl /comm/cable/RS-232.html   (798 words)

 Null Modem Cable DB9 - Cables N Mor, Inc
A null modem cable allows two computers to communicate without a modem.
It allows you to connect your PC to another nearby PC or serial device using its modem protocol.
Cables N Mor > Null Modem Cables > db9 null modem cable
www.cablesnmor.com /null-modem-cable.html   (61 words)

 Interfacing The Serial / RS-232 Port
Considering the high speed of the modem we should expect the DTE to DCE speed to be about 115,200 BPS.(Maximum Speed of the 16550a UART) This is where some people often fall into a trap.
You will most commonly encounter a framing error when using a null modem linking two computers or a protocol analyzer when the speed at which the data is being sent is different to that of what you have the UART set to receive it at.
Bit 0 of the modem status register shows delta clear to send, delta meaning a change in, thus delta clear to send means that there was a change in the clear to send line, since the last read of this register.
www.beyondlogic.org /serial/serial.htm   (4765 words)

 10.5) How do I transfer files using a null modem cable?   (Site not responding. Last check: 2007-10-17)
A convenient way to make a null modem cable, up to about 30 feet long, is to use two female DB25 connectors (Radio Shack) some three or more conductor cable.
A null modem is a small adapter with the correct lines already crossed.
With a null modem, you just plug it into the 25 pin connectors of the two modem cables you might already have connected to your Atari and PC or Mac.
www.faqs.org /faqs/atari-8-bit/faq/section-78.html   (831 words)

 How to set up a remote debug session using a null modem cable
If you connect the null modem cable to a serial port, the debugger can run at its current top speed of 19200, compared to the speed of 9600 over a modem.
A null modem cable is a serial cable that has been configured to allow data to be sent between two serial ports.
It is important that you use a null modem cable because if you use a typical serial cable the target computer expects a serial device, not another serial port, and you cannot debug the computer.
support.microsoft.com /kb/151981   (1462 words)

 The RS232 Standard
For synchronous communications, the null modem cable includes an additional conductor for timing signals, and joins pins 15, 17, and 24 on one side to pins 15 and 17 on the other.
This simplified null modem cable uses only Request-to-Send (pin 4) and Clear-to-Send (pin 5) as handshaking lines; DTE Ready, DCE Ready, and Carrier Detect are not employed, so this cable should not be used with modems.
The modem generates this clock signal to control exactly the rate at which data is sent on Transmitted Data (pin 2) from the DTE device to the DCE device.
www.camiresearch.com /Data_Com_Basics/RS232_standard.html   (5380 words)

 Null Modem Cables ( Null-Modem Cable) Definition
A popular use of null modem cables is for setting up "head-to-head" gaming between two players at different computers in the same room.
NULL MODEM CABLES DEFINITION (continued): … a signal protocol between a Data Terminal Equipment (
For example, the DTE sends the DCE (usually a modem) a "Request to Send" signal on the RTS line and the DCE replies with a "Clear to Send" signal on the CTS line.
www.bitpipe.com /tlist/Null-Modem-Cables.html   (302 words)

 Null Modem Adapters
The intent is to have the ability to create full-handshake RS-232 null modem cables by using pairs of these adapters and four-pair straight-through Cat 5 patch cables (the cables will be procured seperately).
From: Mike Ingram [mailto:mike.ingram@(obscured)] Sent: Tuesday, June 06, 2000 3:35 PM To: bob@drzyzgula.org Subject: question about null modem adapters Hey Bob, I found your response to someone's question about null modem adapters (http://www.eskimo.com/~bob/serial-spec.txt) and I'm confused about something and wondering if you have a couple minutes to help me out.
That is used for the RI (ring indicator) signal from a modem to a computer, and if you're building a null modem adapter, well....
www.drzyzgula.org /bob/electronics/nma.shtml   (1765 words)

Null MODEM construction
  (Site not responding. Last check: 2007-10-17)
A null modem cable is used to transfer files between computers.
The next piece is the 25 pin null modem adapter.
Some programs that you might want to use in conjunction with a null modem cable are
www.syndicomm.com /~gsaug/null/nullmodem.htm   (326 words)

 Ricochet/PalmPilot Modem Connection   (Site not responding. Last check: 2007-10-17)
This is the slimline Null Modem / Gender Changer for connecting the PalmPilot to the Ricochet modem.
One additional advantage of this custom Modem Eliminator design is the freedom from assertion conflicts on DCD which you would suffer from most Null Modems.
The DB25 pinouts are given as a convenience to those wishing to make a 9-25 Null Modem for using a HotSync Cable or Cradle with a standard external modem (which has a DB25-F connector on it).
www.cesium.com /ricochet   (607 words)

 Welcome to Belkin - DB25 Null Modem Adapter
The DB25 Null Modem Adapter converts any straight-through wired cable with DB25 connectors into a null modem “cross-wired” configuration, suitable for many serial PC to PC, and PC to printer, applications.
Converts any straight-through wired cable with DB25 connectors into a null modem cross-wired configuration.
Belkin certifies that this adapter will be free of defects in design, assembly, material and workmanship for a lifetime, or we’ll replace it for free.
catalog.belkin.com /IWCatProductPage.process?Merchant_Id=1&Product_Id=18626   (181 words)

 The Answer Guy 30: Connecting Linux to Win '95 via Null Modem
So, it may not be easy to get networking configured over a null modem line so long as Win '9x is on one end of it.
You should probabl create a "modem emulation" driver for Linux that would allow the Win '9x box to work as though it were sending AT commands to a modem.
You might be able to get it working as a networking interface, but you might have quite a bit of trouble convincing Win '9x to do PPP over a "direct" or "null modem" connection.
www.tldp.org /LDP/LGNET/issue30/tag_nullmodem.html   (964 words)

 Null Modem
To achieve this, the most obvious connection is that the TD signal of one device must be connected to the RD input of the other device (and vice versa).
One of the most common schemes is for the DTE (the PC) to assert the RTS signal if it is ready to receive data (yes, it DOES sound backwards, but that's how it works), and for the DCE (the modem) to assert CTS when it is able to accept data.
If you're using a serial cable or null-modem cable for local serial connectivity or for modem replacement, you might consider looking at the Traversix™ network connectivity solutions.
www.nullmodem.com /NullModem.htm   (476 words)

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