Code Instrument Overview
Appendix C
GPIB-VXI User Manual
C-2
© National Instruments Corporation
GPIB-VXI Operation without CIs
Typical commander/servant relationships for GPIB-VXI operation without CIs are illustrated in
Figure C-1. A GPIB System Controller communicates with the local command set and the
GPIB-VXI's Message-Based servants through GPIB secondary addresses. This is a complete
interface solution for Message-Based devices. Although the GPIB and serial controllers are not
commanders of the command parser in the VXI sense, they are its
master
in the sense that it will
respond to their commands as if they were its commander. The GPIB-VXI maintains
independent control paths to the local command set parser from the GPIB, the serial controller,
and the GPIB-VXI's commander.
The GPIB-VXI has four ports for communicating with other devices. Each port consists of its
electrical interface and the associated system software. The GPIB-VXI communicates with its
commander through the Word Serial servant port, and with its servants through the Word Serial
commander port. The GPIB System Controller communicates with the GPIB-VXI and its
Message-Based servants through the GPIB port, which maps GPIB secondary addresses to VXI
logical addresses. A serial controller can access the local command parser through the RS-232
port, and therefore can communicate with the GPIB-VXI's Message-Based servants through the
Word Serial communication commands.
The System Controller can also directly control Register-Based and non-VXI devices through
the VXIbus Access local commands. This solution to the general problem of controlling
Register-Based and non-VXI devices is relatively ineffective for high-performance applications,
however, because of the low-level functions that the System Controller must perform and the
resulting heavy GPIB traffic.
