Transmission Trigger Timer not started for "Change Of State" and "Application Triggered" Connections

For a class 0/1 connection with trigger type "Change Of State" (COS) or "Application Triggered" (ApplTrig)the device does only sends IO frames on the network for that connection when the host application calls xChannelIoWrite(). Otherwise, the device will not send any process data frames.

According to the specification for COS and ApplTrig connections also the Transmission Trigger Timer applies. In that scenario it is used to maintain the connection so that it does not end up in a timeout.

See CIP Volume 1, Edition 3.32:

Also see:

• 3-4.4.3.6 Client Transport Class 0 and 1 Behavior: Change-Of-State
• 3-4.4.3.8 Client Transport Class 0 and 1 Behavior: Application Object Triggered