DeviceNet write to card by multiple processes

[Olaje]

Do the 8461 DeviceNet cards or associated NI drivers buffer or lockout Poll IO write requests when 2 or more process try to write to the card at essentially the same time?  I see in the documentation that it states the developer must manage request when running parallel processes.  Based on that I assume a lock is uses to block a second request while processing the first write request but I would like to know for sure and not assume.  If a lock is uses is there any indication to when the card is unlocked besides the wait for state command?  Is there any indication that a write request was locked out?  Thanks

[A_Ryan]

Olaje,

Can you please point me to the specific section of the manual that you are referencing so that I can view the same information?

[Olaje]

Hello Ryan,

The only reference to parallel process management in regards to sharing the DNet card/drivers resources that I could find, and the one I am referring to originally, is the NI-Dnet Users Manual, page 3-10 (April 06 version), "Multiple Application on The Same Interface",

Thanks

[DirkW]

Hi,

The NI-Dnet "openDnet I/0" function creates a single ID object for every single device you are calling it for. That means for you got multiple object handles for your devices and you can use them with a single "wait for state" function for every handle in parallel. You cannot use the wait for the same handle multiple times in parallel.

You could run the NI-Spy in parallel to log all your API calls, to see whether a timeout happened to on of your objects. The Spy installs with your NI-DNETdriver.

DirkW

[A_Ryan]

Olaje,

Other D-Net information that could be helpful: DeviceNet Poll Rate , and Get Poll Connection Input & Output Size and Set the Connection Attributes.  If you would like more information please let me know.  Thanks and have a great day

Message Edited by A_Ryan on 01-28-2008 01:01 PM