LX700 - Mainframe - Interface

USB Interface

USB is one of the two standard interface methods for controlling LX700 mainframes through the system software. USB is very common and highly useful as a short range desktop/benchtop bus. USB offers four different modes of data transfer. The LX700 system software employs only Control or Bulk transfer modes. These modes have full error checking and retransmission assuring reliable data.

Ethernet Interface

The Ethernet interface is the other standard means of controlling LX700 mainframes through the system software. Ethernet provides a very flexible and capable interface that allows for large distance between mainframes and the computer.

Each LX700 mainframe also contains a mini web server that can be accessed from any web browser application over the LAN. This is useful for verifying connections, configuration, and status.

GPIB Interface

GPIB (HPIB or IEEE-488) is a short to medium range digital communications bus that has been in use for nearly 50 years. Originally created for use with automated test equipment, the standard is still in wide use today. This is due to the fact that it remains one of the very few methods of controlling, interfacing, and integrating various different types and brands of instrumentation in a uniform and generic fashion.

The GPIB interface is not a primary full function interface used by the LX700 system software. It is intended for use by 3rd party software or custom software created by the user.

The LX700 mainframe does not contain the GPIB Interface as a standard feature. It is provided as an optional interface which can be easily installed by the user. This is a special module installed in the left corner position of the chassis which plugs in directly to the system controller board.

Interface Capabilities

All of the three interface methods Ethernet, USB, and GPIB support multiple mainframes. However each interface differs in the number of mainframes it can support, and the distances which can be covered. The LX700 system software application operated from a single PC can address all of the mainframes and their modules using either the Ethernet or USB interface. The GPIB interface is not a primary interface used by the LX700 software, but intended to be controlled by a 3rd party or custom user application.

• Ethernet is by far the most capable interface allowing up to 250 mainframes and spanning distances of 100 Meters. This interface is ideal for industrial use where the mainframes may be located in a production, warehouse, testing, manufacturing, or remote location, but yet can be controlled from any office workstation anywhere on a LAN (Local Area Network) separated by substantial distance.

• USB is a short range bus, typically 6 Meters, and is appropriate for desktop or benchtop use where the distance to the computer is relatively short. Up to 125 mainframes can be supported.

• GPIB is a medium range bus, typically 20 Meters, and up to 15 mainframes can be supported. However by using multiple GPIB interface cards in the computer more mainframes could be supported. Whether or not this is possible or practical is entirely a function of the software capabilities of the application used.

Large Scale Array Synchronous Sampling

Many applications require a large number of measurements to be performed synchronously. Since all of the LX700 data processing modules contain their own sample memory, data can be transferred back to the computer asynchronously for any number of modules. However, all of the modules involved in a synchronous measurement must be triggered at exactly the same time.

All of the modules within a single mainframe can be triggered synchronously using any of the three interface methods. However, if more than a single mainframe is required, then triggering all of the modules involved across multiple mainframes demands special consideration.

• Ethernet provides extensive ability to perform simultaneous triggering across multiple mainframes. The LX700 software uses the Multicast protocol to trigger all mainframes at the same instant. Timing precision between the mainframe triggers is very precise, with typical variations less than 100nSec.

• GPIB also provides the means to perform simultaneous triggering across multiple mainframes. This is provided by the GET (Group Execute Trigger) command. Timing precision between the mainframe triggers is therefore very precise, with typical variations less than 100nSec.

• USB inherently lacks the ability to address multiple devices simultaneously. In this case, each mainframe will receive the trigger command at different times. The exact amount of latency between commands is unknown and impossible to predict or control. Values range from 1-100 mSec. The USB interface is not a good choice if precision sampling across multiple mainframes is required.