Priorities
Z-Max Advanced Programming & Systems Design Guide rac00-sdg
Revision A:11/2005 Page 65
Priorities
There are many control signals and events all coming into the relay cabinet at the
same time. Priority levels are used to distinguish which event actually occurs when
competing commands are sent.
For example, consider the situation where you want the scheduler to turn the lights
on in a lobby at 7:30am and off at 5:30pm so that the lights are on during business
hours. Also consider for a moment that there is a switch in the lobby which can be
used to turn on/off the lobby lights. Now, consider that the scheduler turns the lights
on at 7:30am but Joe the janitor comes in and presses the switch to turn off the lights
at 7:45am. The lights could remain off all day long! To resolve this problem, priorities
can be used.
Your Z-MAX relay cabinet has (16) priority levels which can be assigned to control
signals and events. 1 is considered to be the highest priority, 16 is considered to be
the lowest priority.
Your Z-MAX relay panel presents a warning when you change the
priority level. This warning is present because simply changing the
priority level of a control signal can drastically change how your panel
operates. Make sure you understand what you’re doing and have a
good reason for doing it. If not….you probably should leave them
alone.
Each relay has a defined state at each priority level:
•
ON
- indicates that the relay should be on at the specified priority level and any
lower priority commands should be ignored
•
OFF -
indicates that the relay should be off at the specified priority level and any
lower priority commands should be ignored
•
RELINQUISH
- indicates that control at the specified priority level is relinquished to
a lower priority level
When a relay determines what state it should be in, it steps through each priority
level and looks for any controlling commands. When it finds one it executes it. If the
command is relinquish, it proceeds to the next priority level. If it steps through all 16
priority levels and finds no on or off commands, then the relay is turned off.
When a signal or event is executed at a priority level, no lower priorities will have any
effect on that relay until control at the higher priority level is relinquished. The control
signal or event will continue to be updated at the lower priority, it just will have no
effect on the relay.
MAIN MENU SELECT
CONFIGURATION
MENU
CONFIGURATION
SYSTEM SETUP
SYSTEM SETUP
PRIORITIES
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