Using and Troubleshooting the GPIB-VXI/C

Getting Started with the GPIB-VXI/C

This document provides on overview of some of the features of the GPIB-VXI/C. The GPIB-VXI/C is a C-sized VXIbus module that links the industry standard IEEE-488 (GPIB) bus or RS-232 serial to the VXIbus. The GPIB-VXI/C performs transparent conversion of the GPIB communication and protocols to VXIbus communication and protocols, so the GPIB Controller can control VXIbus instruments in the same way that it controls GPIB instruments. This makes the GPIB-VXI/C an easy way to add VXIbus components to an existing GPIB system. By default, you communicate to the GPIB-VXI/C at GPIB primary address 1 and secondary address 0 (96 using NI-488 commands). You can change the GPIB primary and secondary addresses through the non-volatile configuration.

The GPIB-VXI/C is factory configured to function as the system Resource Manager (RM). It performs the VXIbus startup configuration, self-test, and initialization functions, as well as VXIbus Slot 0 related services. By default, the logical address of the GPIB-VXI/C is 0, and the job of LA0 is to run Resman which is done by the processor on the GPIB-VXI/C during boot-up. You can see the output of Resman through the serial interface using Hyperterminal or any other terminal program if Switch S11 is pushed to the Printing Enabled position (please refer to the section on setting up the serial interface).

GPIB Address Assignment
In its default state, the GPIB-VXI/C assigns a secondary GPIB address to message-based VXI devices by taking its logical address, dividing by eight, and truncating. If the calculated secondary GPIB address has already been assigned to another device, the next higher available secondary GPIB address is assigned to the device. The GPIB-VXI/C assigns secondary GPIB addresses only to Message-Based VXIbus devices. The host GPIB controller can directly access Message-Based devices by using the primary address of the GPIB-VXI/C and the secondary GPIB addresses assigned by the GPIB-VXI/C, as if the VXI device was any other GPIB instrument. To access Non-Message-Based devices (register-based devices), the host GPIB controller must issue local commands to the GPIB-VXI/C, which interprets the commands to determine the operation to perform on the VXIbus.

Furthermore, suppose that an instrument is assigned a primary and secondary address of 1 and 2, respectively. When using VISA, the GPIB primary and secondary addresses would be 1 and 2, respectively. However, when using the Win32 Interative Control (IBIC) program provided by the National Instruments GPIB driver, a value of 96 should be added to the secondary address to open a session to a message based device. The table below illustrates this situation.

	VISA API		NI-488 API
Logical Address of Message-Based Instrument	GPIB Primary Address	GPIB Secondary Address	GPIB Primary Address	GPIB Secondary Address
0	1	0	1	96
24	1	3	1	99
33	1	4	1	100

In LabVIEW, when using the 488.1 VIs, the secondary addressing is similar to VISA's. Note that the address string is made as follows:

(GPIB board index) : (primary address) + (secondary address).

GPIB Addressing using GPIB VIs (488.1)

GPIB Addressing using 488.2 VIs