Overview

This profile simplifies event-driven monitoring by a controller. There are three common methods for a controller to monitor network variables in an ISI network: polling, controlled enrollment, and automatic enrollment. The advantage of polling is that it does not require any additional code in the monitored devices, but the disadvantage is that the controller may require a long time to poll all network variables in a network--this may cause the controller to appear to have a poor response time after a network variable value on a monitored device changes. Controlled and automatic enrollment both address responsiveness by supporting event-driven updates-the controller is notified whenever a monitored network variable value changes. The disadvantage of both controlled and automatic enrollment is that additional code space is required on the monitored device, with automatic enrollment requiring the most code space. Controlled enrollment typically requires less code than automatic enrollment on a device that does not already use automatic enrollment; automatic enrollment typically requires less code on a device that uses automatic enrollment for other connections. Automatic enrollment gives more control to the monitored device and requires fewer network transactions to set-up than automatic enrollment.

The automatic enrollment method requires the monitored device to support automatic connections and connection replacement, and also requires the device to be more involved in creating the monitored connection--the monitored device determines which network variables on the device will be connected to the controller. For a controller to use automatic enrollment for monitoring, the controller becomes the automatic connection host for data used by the controller. The controller uses this profile for the functional block and network variable that it offers in the automatic enrollment invitation.