Allen-Bradley GuardLogix 5580 Original Instructions Manual page 104

Glossary
instruction signature The instruction signature consists of an ID number and date/time stamp that
identifies the contents of the Add-On Instruction definition at a given point in
time.
lambda (λ) Designation of a failure rate.
MT (mission time) The length of time over which the device maintains the stated PFD, PFH, and
λ ratings before replacement is required.
network delay multiplier This value represents the transport time of a message across the
communication network. See also timeout multiplier.
nonrecoverable controller fault A fault that forces all processing to be ended and requires controller power to
be cycled from off to on. The user program is not preserved and must be
redownloaded.
nonrecoverable safety fault A fault, which even though properly handled by the fault handling
mechanisms that are provided by the safety controller and implemented by the
user, ends all safety task processing, and requires external user action to restart
the safety task.
online Situation where you are monitoring/modifying the program in the controller.
overlap When a task (periodic or event) is triggered while the task is still executing
from the previous trigger.
partnership The primary controller and safety partner must both be present in SIL 3, and
the hardware and firmware must be compatible for partnership to be
established.
pending edits A change to a routine that has been made in the Studio 5000 Logix Designer
application, but has not yet been communicated to the controller by accepting
the edit.
Performance Level (PL) The discrete level that is used in the EN ISO 13849-1, to specify the ability of
safety-related parts of control systems to perform a safety function under
foreseeable conditions.
periodic task A task that the operating system triggers at a repetitive period. Whenever the
time expires, the task is triggered and its programs are executed. Data and
outputs that the programs in the task establish retain their values until the next
execution of the task or until another task manipulates them. Periodic tasks
always interrupt the continuous task.
personal computer (PC) Computer that is used to interface with and control a Logix-based system via
the Studio 5000 environment.
primary controller The processor in a dual-processor controller that performs standard controller
functionality and communicates with the safety partner to perform safety-
related functions.
104
Rockwell Automation Publication 1756-RM012B-EN-P - April 2018