Справочник Пользователя для National Instruments NI-DNET

© National Instruments Corporation

2.

Call the 

ncWaitForState

 function with the 

DesiredState

 

parameter set to 

Read Available

. This function waits for output 

data to be transmitted and for new input data to be received. If your 
application is multitasking, you might have other tasks to do in your 
application while you wait for new input data. If so, use the 

ncCreateNotification

 or 

ncCreateOccurrence

 function 

instead of 

ncWaitForState

 (refer to 

).

3.

Call the 

ncReadDnetIO

 function to read input data received from the 

DeviceNet network.

4.

Loop back to step 1 as needed.

Complete the following steps with an Explicit Messaging Object:

1.

Call the 

ncWaitForState

 function with the 

DesiredState

 

parameter set to 

Established

.  This ensures that the explicit message 

connection is established before you send the first explicit message 
request.

2.

To get an attribute from a remote DeviceNet device, call the 

ncGetDnetAttribute

 function.

3.

To set the value of an attribute in a remote DeviceNet device, call the 

ncSetDnetAttribute

 function.

4.

To invoke other explicit message services in a remote DeviceNet 
device, use the 

ncWriteDnetExplMsg

 function to write the service 

request, the 

ncWaitForState

 function to wait for the service 

response, and the 

ncReadDnetExplMsg

 function to read the service 

response.

5.

Loop back to step 2 as needed.

If you need to add I/O and Explicit Messaging connections after the 
communication on the network has started, you can call 

ncOpenDnetExplMsg

 and 

ncOpenDnetIO

 as long as the Interface 

Object’s poll mode had been configured to 

NC_POLL_SCAN

 (Scanned) or 

NC_POLL_INDIV

 (Individual). Since the Automatic poll mode 

(

NC_POLL_AUTO

) calculates the expected packet rate (EPR) based on the 

estimated network bandwidth, all the I/O connections have to be opened 
before you start the communication if the Automatic mode is selected. The 
EPR restrictions due to different values of the 

PollMode

 parameter still 

apply to the I/O objects. For details on these requirements, refer to 

ncOpenDnetIO

 and 

ncOpenDnetIntf

 function descriptions in the 

NI-DNET Programmer Reference Manual.