Hardware Overview

The GPIB-140B is a high-speed bus extender that you can use in pairs with multi-mode fiber-optic cable to connect two separate GPIB systems in a functionally transparent manner.

The two bus systems are physically separate, as shown in the following figure.

The devices logically appear to be located on the same bus, as shown in the following figure.

The bus extender complies with the specifications of the ANSI/IEEE Standard 488.1-1987 and the ANSI/IEEE Standard 488.2-1992, including the Find Listeners protocol. With the GPIB extenders, you can overcome the following two configuration restrictions imposed by IEEE 488:

• A cable length limit of 20 m total per contiguous bus or 2 m per each device on the bus, whichever is smaller.
• An electrical loading limit of 15 devices per contiguous bus.

Each GPIB-140B system extends the GPIB to a maximum distance of 1 km, and extends the loading limit to 28 devices (including the GPIB extenders), without sacrificing speed or performance. You can connect these point-to-point extension systems in series for longer distances or in star patterns for additional loading.

Using the HS488 protocol, the maximum data transfer rate over the extension is greater than 2.8 MBytes/s. The GPIB extenders use a buffered transfer technique with a serial extension bus, which maximizes performance and minimizes the cabling cost. Furthermore, the extender does not affect the transfer rate between devices on the same side of the extension. The GPIB extender can also check for errors to make sure that the data transmitted successfully over the fiber-optic link.

Because the GPIB-140B is a functionally transparent extender, the GPIB communications and control programs that work with an unextended system also work with an extended system. However, the Parallel Poll Response Modes section describes one exception to this transparency in conducting parallel polls.