protocol converter

Definition of protocol converter in The Network Encyclopedia.

What is Protocol Converter?

A general term for a device that enables communication between networks or transmission systems that use different protocols. Protocol converters are often used in mainframe computing environments; they enable one device to emulate the communication functions of another device. For this reason, a protocol converter is sometimes known as an emulator, and it can be either hardware-based or software-based.

How It Works

One type of protocol converter allows you to communicate asynchronously using a PC to a mainframe host over a synchronous communication link. You can thus use a PC as the front end to the host instead of using expensive synchronous terminals. The PC typically emulates a 3270 terminal for remote connections or a 5250 terminal for local connections.

For example, you can turn a PC into a 5250 terminal by installing a 5250 emulator card. Use twinax cabling to connect the port on the card directly to the AS/400 or System 390 mainframe. The 5250 emulator software running on the PC typically supports multiple concurrent 5250 sessions.

To support this synchronous/asynchronous conversion, the emulation hardware/software must perform several conversions:

  • Connect the twinax or coax synchronous connection from the host to an asynchronous RS-232 connection for the PC. For a remote connection, the converter might include X.21 or V.35 serial interfaces as well.

Graphic P-13. Protocol converter.

  • Take the Synchronous Data Link Control (SDLC) data stream from the host and convert it to an asynchronous format.
  • Perform synchronous EBCDIC to asynchronous ASCII conversion and translate standard input/output into appropriate screen/keyboard mappings.

You can also use protocol converters to connect ASCII printers to AS/400 or System/3x mainframe hosts. A protocol converter for this purpose is sometimes called a printer emulation card.