Using Multiple Interfaces And/Or Multiple Devices; Checking Status With Global Variables; Status Word (Ibsta) - National Instruments NI-488.2 User Manual

Checking Status with Global Variables

Note If your application is a multithreaded application, refer to the section
Multithreaded Win32 NI-488.2 Applications
Techniques.

Status Word (ibsta)

© National Instruments Corporation
Board-level functions that an NI-488.2 application might use include the
following— ,
ibcmd ibrd
to the NI-488.2 online help. For instructions on accessing the online help,
refer to the Using the NI-488.2 Documentation
Manual.

Using Multiple Interfaces and/or Multiple Devices

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
• Find a device requesting service using
• Determine the state of the SRQ line, or wait for SRQ to be asserted
using or
TestSRQ
• Address multiple devices to receive a command using
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
variables ( and
ibcnt
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.
All NI-488.2 calls update a global status word,
information about the state of the GPIB and the GPIB hardware. The value
stored in is the return value of all the traditional NI-488.2 calls,
ibsta
except and
ibfind ibdev
and use that information to make decisions about continued processing. If
Chapter 3
, , and
ibwrt ibconfig
FindLstn
.
WaitSRQ
), the error variable (
). They contain useful information about the
ibcntl
in Chapter 7, NI-488.2 Programming
. You can examine various status bits in
3-5
Developing Your NI-488.2 Application
. For a detailed list, refer
section in About This
.
.
FindRQS
SendList
), and the count
iberr
Writing
, which contains
ibsta
NI-488.2 User Manual for Windows
.
ibsta