National Instruments NI-488.2 Benutzerhandbuch

© National Instruments Corporation

Board-level functions that an NI-488.2 application might use include the 
following—

ibcmd

, 

ibrd

, 

ibwrt

, and 

ibconfig

. For a detailed list, refer 

to the NI-488.2 online help. For instructions on accessing the online help, 
refer to the 

 section in 

When your system includes an interface that must access multiple devices, 
use the multi-device NI-488.2 calls, which can perform the following tasks 
with a single call:

•

Find the Listeners on the bus using 

FindLstn

.

•

Find a device requesting service using 

FindRQS

.

•

Determine the state of the SRQ line, or wait for SRQ to be asserted 
using 

TestSRQ

 or 

WaitSRQ

.

•

Address multiple devices to receive a command using 

SendList

.

You can mix board-level traditional NI-488.2 calls with the multi-device 
NI-488.2 calls to have access to all the NI-488.2 functionality.

Each NI-488.2 API call updates four global variables to reflect the status of 
the device or interface that you are using. These global status variables are 
the status word (

ibsta

), the error variable (

iberr

), and the count 

variables (

ibcnt

 and 

ibcntl

). They contain useful information about the 

performance of your application. Your application should check these 
variables after each NI-488.2 call. The following sections describe each of 
these global variables and how you can use them in your application.

If your application is a multithreaded application, refer to the section 

 in Chapter 7, 

. 

All NI-488.2 calls update a global status word, 

ibsta

, which contains 

information about the state of the GPIB and the GPIB hardware. The value 
stored in 

ibsta

 is the return value of all the traditional NI-488.2 calls, 

except 

ibfind

 and 

ibdev

. You can examine various status bits in 

ibsta

 

and use that information to make decisions about continued processing. If