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Chapter 8 NI-488.2 Programming Techniques

A quick way to convert your application to use per-thread NI-488.2 globals

is to add the following

#define lines at the top of your C file:

#define ibsta ThreadIbsta()

#define iberr ThreadIberr()

#define ibcnt ThreadIbcnt()

#define ibcntl ThreadIbcntl()

Note

If you are using ibnotify in your application (refer to the Asynchronous Event

Notification in NI-488.2 Applications section of this chapter), the

ibnotify callback

is executed in a separate thread that is created by the NI-488.2 driver. Therefore, if your

application makes NI-488.2 calls from the

ibnotify callback function and makes

NI-488.2 calls from other places, you must use the

ThreadIbsta, ThreadIberr,

ThreadIbcnt, and ThreadIbcntl functions described in this section, instead of the

per-process NI-488.2 globals.

Device-Level Calls and Bus Management

The device-level traditional NI-488.2 calls are designed to perform all

of the GPIB management for your application. However, the NI-488.2

driver can handle bus management only when the GPIB interface is CIC

(Controller-In-Charge). Only the CIC is able to send command bytes to the

devices on the bus to perform device addressing or other bus management

activities.

If your GPIB interface is configured as the System Controller (default),

it automatically makes itself the CIC by asserting the IFC line the first

time you make a device-level call.

If the current CIC does not pass control, the NI-488.2 driver returns the

ECIC error code to your application. If this happens, you could send

a device-specific command requesting control for the GPIB interface.

Then, use a board-level

ibwait command to wait for CIC.

National Instruments NI-488.2 NI-488.2 User Manual

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