Echelon LonPoint Application and Plug-In - Manual (Page 12)

1-6 LonPoint System Overview
L ON M ARK Certified: Yes
The DI-10 device’s version 2 and version 3 applications have different Device Class
values, so the LonMaker tool will issue a warning when an attempt is made to load a
version 3 DI-10 application into a device which currently contains a version 2 DI-10
application. This warning may be safely ignored.
The SCH-10 device supports two applications, the SCH-10 application and the DL-10
application. Attempting to load the DL-10 application into a SCH-10 device which
currently contains the SCH-10 application or vice versa will cause a warning in the
LonMaker tool that an attempt is being made to load an application with a different
Device Class or Device Subclass into a device already containing an application. In
this case, this warning may be safely ignored.
Terminology Used in this Manual
The following sections contain definitions for several concepts presented in this
manual in conjunction with the LonPoint functional blocks.
Upstream and Downstream
The terms upstream and downstream represent the flow of information. If
functional block A sends information to functional block B, B is said to be
downstream of A, and A is said to be upstream of B. For example, in the following
figure, the DO- 1 Valve Actuator is downstream of the DI- 1 Limit Switch.
Heartbeats
A heartbeat is a network variable update that is automatically sent if the network
variable has not otherwise been updated for a configurable length of time.
Most LonPoint output network variables can be configured to send heartbeat
updates. Most LonPoint input network variables can monitor heartbeats from
upstream functional blocks to detect device failures using heartbeat receive
checking. If a heartbeat is not received within the specified amount of time, the
functional block will go into heartbeat failure and cease propagating output network
variables, and if the functional block is associated with a hardware output it will
cause that output to go to its configured default value. The functional block will
return to normal operation once the heartbeat is restored.
The heartbeat send time should be approximately 4 times as frequent as the
corresponding expected heartbeat receive time to allow for lost messages.
Heartbeat failure propagates downstream in a LonPoint system. Once a LonPoint
functional block receives a heartbeat failure, it will stop sending heartbeats, causing