User Manual

Calendars and schedulers
Schedule
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The information flows inside one automation station or across several automation stations. The scheduler
object recognizes the flow of information and knows where to send information and what data type is
required by the group members. The information transmitted covers only the present value [PrVal] or the
values for the Optimum Start/Stop functions [PrVal], [NxVal] and [NxTi].
Heartbeat [Hrtbt]
In Desigo PX the function block variable Heartbeat [Hrtbt] determines the period measured in seconds at
which the current value (Present_Value) is written.
Enable_Repeat_
Command [EnRptCmd]
In Desigo PX the function block variable Enable_Repeat_Command [EnRptCmd] defines if the switching
action is executed if the Present_Value does not change:
● EnRptCmd = TRUE: Switching action is executed if Present_Value does not change.
● EnRptCmd = FALSE: Switching action is NOT executed if Present_Value does not change.
Effective period [EfPrd]
You can define the period for which the schedule is to be active, e.g., you can configure separate schedules
for summer and winter operation. If the current day is outside the active period, the [PrVal] output is equal
to the default value [DefVal].
Time resolution
The smallest unit in the scheduler program is one minute and in the calendar one day. The schedule may
be dependent on the calendar. In the PX automation stations, the calendar function block is automatically
processed before the scheduler function block. The superposed cycle for processing the calendar and
scheduler begins at the start of the new minute of the system time.
A PX automation station incorporates an automatic load shedding mechanism. The result is that a switch
command at time x is executed within a time-period defined by time x + 1 minute.
System time
Schedules and calendars are based on the same global time. This ensures that all automation stations on a
site have the same time base.
Interdependency and order of processing
Interdependency of function blocks
The calendar and schedule function blocks are standalone objects which are processed individually. The
Schedule function blocks depend on the Calendar function blocks. The objects to be switched (commanded
objects or data flow output) depend on the Schedule function blocks.