Справочник Пользователя для National Instruments NI-DNET

Before you use an NI-DNET object in your application, you must configure 
and open it using either 

ncOpenDnetIntf

, 

ncOpenDnetExplMsg

, or 

ncOpenDnetIO

. These open functions return a handle for use in all 

subsequent NI-DNET calls for that object.

The 

ncOpenDnetIntf

 function configures and opens an Interface Object. 

Your NI-DNET application uses this Interface Object to start and stop 
communication. The Interface Object must be the first NI-DNET object 
opened by your application.

The 

ncOpenDnetExplMsg

 function configures and opens an Explicit 

Messaging Object, and the 

ncOpenDnetIO

 function configures and opens 

an I/O Object.

Start communication to initialize DeviceNet connections to remote 
devices. Use the Interface Object to call the 

ncOperateDnetIntf

 

function with the 

Opcode

 parameter set to 

Start

.

The following optional steps can be done before you start communication:

•

For an I/O Object, if it is not acceptable to send output data of all zeros, 
call 

ncWriteDnetIO

 to provide valid output values for the initial 

transmission.

•

For an I/O Object, if your application is multitasking, call the 

ncCreateNotification

 or 

ncCreateOccurrence

 function with 

the 

DesiredState

 parameter set to 

Read Available

. This notifies 

your application when new input data is received from the remote 
device.

•

For any NI-DNET object, if any of the Driver attributes needs to be 
changed, call 

ncSetDriverAttr

 with the attribute Id and attribute 

value. The 

ncSetDriverAttr

 function cannot be called after the 

communication has started.

After you open your NI-DNET objects and start communication, you are 
ready to interact with the DeviceNet network.

Complete the following steps with an I/O Object:

1.

Call the 

ncWriteDnetIO

 function to write output data for subsequent 

transmission on the DeviceNet network.