Echelon LonPoint Application and Plug-In - Manual (Page 120)

10-18 Scheduler Interface
Defining Exit Conditions
An exit condition is a specification for the conditions under which a transition
should be followed in a state machine. An exit condition is defined as a
combination of events from the Event Scheduler functional block and the values
of the State Machine functional block’s input network variables.
An exit condition is defined as a logical expression consisting of multiple terms
separated by AND and OR. Each term is an expression with a True or False
result. There are four types of terms: analog, mode input, digital input, and
scheduler. Following is a description of each type:
•
An analog term is an expression based on arithmetic operations and
comparisons on the analog network variable inputs to the State Machine
functional block. The network variable inputs are defined on your Analog
Inputs shape as described earlier in this chapter. An analog term may
include any number of the analog inputs, floating point numbers, and one
comparison function.
For example, an analog term is defined to return True if the average
temperature from two temperature sensors is equal to or above 25º C. The
term would be defined as the following expression:
((iTempSens1 + iTempSens2)/2) >= 25
Note: Operations on analog inputs are performed on the raw analog data in
units native to the network variable. For example, operations on a variable
of type SNVT_temp_f will always use units of “degrees Celsius,” even if the
system has been configured to display data in U.S. units.
•
A mode input term compares the Mode input network variable to one of its
possible values. The expression can specify that the Mode input “Is” or “Is
Not” equal to a possible Mode value. Following are two examples:
Mode IS HVAC_AUTO
Mode IS NOT HVAC_WARMUP
•
A digital input term specifies that one of the digital inputs to the State
Machine functional block is equal to ON or OFF. The digital inputs are
declared as SNVT_Switch inputs. A SNVT_Switch input has two fields, a
value expressed as a percentage, and a state expressed as a 0 or 1. If either
field is 0, the input value is considered OFF, otherwise it is considered ON.
Following are two examples:
iSystemEnable ON
iEmergency OFF
•
A scheduler input term specifies an event defined for the Event Scheduler
functional block. Following are two examples:
evtOccupied ON