Serial data control cable

The schematic below is used to make a half duplex RS monitoring cable. This cable is used for monitoring 2 devices that send data in half duplex. For example, one device sends data and another devices wait for incoming data. A straight-through cable is used to connect a DTE e. A crossover null-modem cable is used to connect two DTE directly, without a modem in between. They cross transmit and receive data signals between the two sides and there are many variations on how the other control signals are wired, below is one of them:.

RS connects the Ground of 2 different devices together, which is the so-called "Unbalanced" connection. An unbalanced connection is more susceptible to noise, and has a distance limitation of 50 ft which is around 15 meters. A protocol is one or a few sets of hardware and software rules agreed to by all communication parties for exchanging data correctly and efficiently.

Synchronous Communication requires the sender and receiver to share the same clock. The sender provides a timing signal to the receiver so that the receiver knows when to "read" the data. Synchronous Communication generally has higher data rates and greater error-checking capability.

A printer is a form of Synchronous Communication. Asynchronous Communication has no timing signal or clock. As it uses less wires for communication no clock signals , Asynchronous Communication is simpler and more cost-effective. Internal computer communications consists of digital electronics, represented by only two conditions: ON or OFF.

We represent these with two numbers: 0 and 1, which in the binary system is termed a Bit. A Byte consists of 8 bits, which represents decimal number 0 to , or Hexadecimal number 0 to FF.

As described above, a byte is the basic unit of Asynchronous communications. The baud rate is the communication speed that measures the number of bit transfers per second. For example, baud is bits per second.

Data bits are a measurement of the actual data bits in a communication packet. For example, the above graphic shows eight 8 data bits in a communication packet. Parity is a simple way to error-check. Also the handshaking must be set the same for the printer to print at all. You can change the interface settings of the printer using theDIPswitches on the underside of the printer. See the support page for the model of printer you are using for specific switchsettings. Verify the port you are using by checking the port in the DeviceManager under the System applet in the Windows Control Panel.

Configuring the Printer inWindows First off, it should be said that the serial printer is not Windows plug and playcompliant. You need to make a few changes in the printer settings in Windows to get it to workwith the serial adapter.

Specifically you need to configure the serial port you areusing to connect with the printer. Open the printer in the Windows Printer Folder. Select the Ports Tab. Turn off bidirectional support, if experiencing problems printing. You can try selecting the serial port in use COM4in the above example.

Press the 'Configure Port' button to open the properties screen. Enter the same settings as were printed out in the adapter self-test. We recommend that you run off the 'bidirectional printing' option on the Portsscreen. Installing the Printer Driverin Windows After installing the drivers, the printer should be visible in the printers folder of the Windows ControlPanel. Testing the Printer You should now be ready to test the printer by printing some text or by pressingthe 'Print Test Page' button in the General Tab of the printer properties.

Port settings are set the sameon the printer from the Self Test and in Windows. The data cable has the rightconfiguration for the printer and computer in use. Using the wrong datacable is the most common problem with new installations. It defines the electrical properties and the timing of signals, as well as the interpretation of signals, and the physical size and pinout configuration of a connector. Modern day computers seldom have RS ports.

These shortcomings include low transmission speed, limited cable length, substantial voltage fluctuations, and limited multidrop capabilities. It is however possible to use an external USB-to-RS converter or an internal expansion card with one or more serial ports to connect a RS serial peripheral device to your computer.

Many motherboards also feature a COM port header which makes it possible to install a bracket with a DE-9 port. Despite the shortcomings and the technology advancements, RS interfaces are still very much in use with large industrial machines, networking equipment and scientific instruments where point to point, low speed wired data connections is sufficient.

A PC serial port interface is single ended. This means that you can only connect two devices using a RS serial cable. The data that is transferred between these two devices is transferred at a rate less than 20 kbps. RS allows for full-duplex communication — this means that both devices can interface with each other simultaneously.

A common ground between the computer and the connected serial device is mandatory. This is represented by voltage levels defined by the RS protocol. With RS, hot-plugging or hot-swapping is not supported, though it is sometimes possible to plug in a serial device and it will work while the computer is running.