Echelon ISI User Manual

Page 93

ISI Programmer’s Guide

device to a peer-to-peer connection. To support controlled enrollment, the

controller must maintain a device description table that lists:

• the program IDs that support controlled enrollment,

• which network variables on each of those devices are to be monitored by

the controller,

• the assembly containing each monitored network variable, and

• which of the devices support connection replacement and which support

connection extension.

For devices with program IDs that are not in the device description table, the

controller may query the device for the required information. The controller can
query and interpret the device’s node self-documentation string to get a list of the

functional blocks implemented by the device, then use the standard functional

profiles to determine the required network variables, and then use the standard
assembly number to functional block number mapping described in

ISI

Connection Model

in Chapter 2 to determine the assemblies.

To support controlled enrollment for monitoring, a controller follows these steps

upon discovering a device as described in

Discovering Devices

in this chapter:

1. The controller looks up the discovered device in the device description

table and determines whether it supports controlled enrollment,

connection replacement, and/or connection extension.

2. If the device supports controlled enrollment and connection extension, the

controller extends any existing connection for the monitored assembly by

sending isiOpen and isiExtend requests to the device, and then recovers

connections to confirm that the connection was successfully extended. If
the connection was not successfully created, the controller proceeds with

the remaining steps.

3. If the device supports controlled enrollment and connection replacement,

but does not support connection extension or could not extend the
existing connection, the controller determines if the monitored NV is

already in a connection. It does this by using connection recovery as

described in

Recovering Connections

in this chapter. If the monitored NV

is not already in a connection, the controller creates a connection from the

monitored NV to the controller using the isiOpen and isiCreate requests.
If the monitored NV is already in a connection, the controller rebuilds the

connection using the isiOpen and isiCreate requests on all assemblies in

the connection, adding the controller to the connection.

4. If the device supports controlled enrollment but does not support

connection replacement or connection extension, the controller

determines if the monitored NV is already in a connection. It does this by

using connection recovery as described in

Recovering Connections

in this

chapter. If the monitored NV is not already in a connection, the

controller creates a connection from the monitored NV to the controller

using the isiOpen and isiCreate requests. If the monitored NV is already
in a connection, the controller sends the isiFactory request to the device

to clear all of its existing connections, and then rebuilds all connections