IFM Electronic Ecomat Mobile Series System Manual page 284

Glossary of Terms
environment. The devices must not interfere
with their environment and must not be
adversely influenced by external
electromagnetic interference.
Ethernet
Ethernet is a widely used, manufacturer-
independent technology which enables data
transmission in the network at a speed of 10 or
100 million bits per second (Mbps). Ethernet
belongs to the family of so-called "optimum
data transmission" on a non exclusive
transmission medium. The concept was
developed in 1972 and specified as
IEEE 802.3 in 1985.
EUC
EUC = "Equipment Under Control"
EUC is equipment, machinery, apparatus or
plant used for manufacturing, process,
transportation, medical or other activities
(→ IEC 61508-4, section 3.2.3). Therefore, the
EUC is the set of all equipment, machinery,
apparatus or plant that gives rise to hazards
for which the safety-related system is required.
If any reasonably foreseeable action or
inaction leads to hazards with an intolerable
risk arising from the EUC, then safety functions
are necessary to achieve or maintain a safe
state for the EUC. These safety functions are
performed by one or more safety-related
systems.
F
Failure
Failure is the termination of the ability of an
item to perform a required function.
After a failure, the item has a fault. Failure is
an event, fault is a state.
The concept as defined does not apply to
items consisting of software only.
Failure, dangerous
A dangerous failure has the potential to put the
SRP/SC in a hazardous or fail-to-function
state. Whether or not the potential is realized
can depend on the channel architecture of the
system; in redundant systems a dangerous
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hardware failure is less likely to lead to the
overall dangerous or fail-to-function state.
Failure, systematic
A systematic failure is a failure related in a
deterministic way (not coincidental) to a certain
cause. The systematic failure can only be
eliminated by a modification of the design or of
the manufacturing process, operational
procedures, documentation or other relevant
factors.
Corrective maintenance without modification of
the system will usually not eliminate the failure
cause.
Fault
A fault is the state of an item characterized by
the inability to perform the requested function,
excluding the inability during preventive
maintenance or other planned actions, or due
to lack of external resources.
A fault is often the result of a failure of the item
itself, but may exist without prior failure.
In ISO 13849-1 "fault" means "random fault".
Fault tolerance time
The max. time it may take between the
occurrence of a fault and the establishment of
the safe state in the application without having
to assume a danger for people.
The max. cycle time of the application program
(in the worst case 100 ms, → Watchdog,
→ page 44) and the possible delay and
response times due to switching elements
have to be considered.
The resulting total time must be smaller than
the fault tolerance time of the application.
Firmware
System software, basic program in the device,
virtually the operating system.
The firmware establishes the connection
between the hardware of the device and the
user software. This software is provided by the
manufacturer of the controller as a part of the
system and cannot be changed by the user.