User manual

106 Publication 1756-RM093F-EN-P - January 2010
Glossary
Safety Program
A safety program has all the attributes of a standard program, except
that it can only be scheduled in a safety task. The safety program
consists of zero or more safety routines. It cannot contain standard
routines or standard tags.
Safety Routine
A safety routine has all the attributes of a standard routine except that
it is valid only in a safety program and that it consists of one or more
instructions suitable for safety applications (See Appendix
A for a list
of Safety Application Instructions and standard Logix Instructions that
may be used in safety routine logic.)
Safety Tags
A safety tag has all the attributes of a standard tag except that the
GuardLogix controller provides mechanisms certified to SIL 3 to
ensure the integrity of their associated data. They can be
program-scoped or controller-scoped.
Safety Task
A safety task has all the attributes of a standard task except that it is
valid only in a GuardLogix controller and that it may schedule only
safety programs. Only one safety task can exist in a GuardLogix
controller. The safety task must be a periodic/timed task.
Safety Task Period
The period at which the safety task executes.
Safety Task Reaction Time
The sum of the safety task period plus the safety task watchdog. This
time represents the worst case delay from any input change presented
to the GuardLogix controller until the processed output is available to
the producing connection.
Safety Task Signature
A value, calculated by the firmware, that uniquely represents the logic
and configuration of the safety system. It is used to verify the integrity
of the safety application program during downloads to the controller.