What does a null modem cable do?

What does a null modem cable do?

A null modem is a specially designed cable that allows a “head-to-head” connection between two nearby serial devices (computers) through their communication ports (RS-232).

How do I know if my RS-232 cable is null modem?

To tell if your NI serial cable is null modem or straight though, search for its part number in NI Serial Hardware Specifications and Features and note the cable type in the description. Alternatively, you can use a handheld DMM to test continuity on the individual pins of your serial cable.

What is null modem configuration?

The null modem configuration is used to connect two hosts together directly. There are no modems required. See Appendix B, Modem and Null Modem Cables for a description of the null modem cables that can be used for this configuration.

Is a null modem cable straight through?

The pinout of the serial connectors on both sides of the cable are exactly the same with a straight-through serial cable. A null modem serial cable (frequently called a crossover cable) is used to connect two DTE devices together without the use of a DCE device in between.

Are there different types of RS232 cables?

The RS-232 specification defines two types of serial devices, DTE and DCE. DTE normally refers to the serial port on a PC or terminal, while DCE refers to a modem or other type of communications device.

What is the purpose for the RS-232 null modem connection?

A null-modem connection is a connection created via RS232 protocol between two computers without a modem. Initially, the RS-232 standard was intended for connecting a teletype with a telephone modem. By means of modems, teletypes communicated with each other.

What is a DB9 null modem cable?

Null modem cables are serial cables that use an alternative pinout for different functionality. A standard DB9 AT cable pinout (non-null modem) Originally, all serial cables were AT cables and could not connect two devices (such as two computers) directly.

How many wires does RS-232 use?

The RS-232 Standard Although RS-232 does not specify connector configurations, two have become de facto standards: DB25 (a 25-pin connector, in which usually no more than 10 wires are used), and DB-9 (a 9-pin connector, in which usually all 9 wires are used).

How can you tell the difference between a serial cable and a null modem?

Are all RS-232 cables the same?

The only problem is the large variety of RS232 null modem cables available. For simple connections, a three line RS232 cable connecting the signal ground and receive and transmit lines is sufficient. Depending of the software used, some sort of handshaking may however be necessary.

What is a RS-232 cable?

RS232 is a standard protocol used for serial communication, it is used for connecting computer and its peripheral devices to allow serial data exchange between them. As it obtains the voltage for the path used for the data exchange between the devices.

How many wires are in a RS-232 cable?

What type of signal is RS-232?

RS-232 signals are similar to your microcontroller’s serial signals in that they transmit one bit at a time, at a specific baud rate, with or without parity and/or stop bits. The two differ solely at a hardware level.