Page 273 - Electrical Engineering Dictionary

fail safe pertaining to a circuit, for a set of false color the replacement of a color in
faults, ifandonlyifforanyfaultinthissetand a colored image by a different color, usually
for every valid input code either the output is not present in the original image. Used to
correct or assumes some defined safe state. highlight regions or distinguish pixels of sim-
ilar colors. See also pseudo color.
fail-stop processor a processor that does
not perform incorrect computation in the false sharing the situation when more
event of a fault. Self-checking logic is of- than one processor accesses different parts of
ten used to approximate fail-stop processing. the same line in their caches but not the same
data words within the line. This can cause
failure manifestation of an error at system significant performance degradation because
level. Itrelatestoexecutionofwrongactions, cache coherence protocols consider the line
nonexecutionofcorrectactions, performance as the smallest unit to be transferred or inval-
degradation, etc. idated.

failure mechanism a physical or chem- fan beam reconstruction reconstruction
ical defect that results in partial degradation of a computed tomography image from pro-
or complete failure of a product. jections created by a point source that emits
a fan- or wedge-shaped beam of radiation.
Fan beam reconstruction enables data to be
fairness (1) the concept of providing
gathered much more quickly than by using
equivalent or near-equivalent access to a
a linear beam to produce parallel projec-
shared resource for all requestors.
tions. See also computed tomography, image
(2) a fair policy requires that tasks,
reconstruction, projection, Radon transform.
threads, or processes are allowed access to
a resource for which they compete.
fan-in (1) the number of inputs to a mod-
(3) the degree to which a scheduling or al- ule. This is usually used in connection with
location policy is equitable and nondiscrimi- logic gates.
natory in granting requests among processes
(2) multiple inputs of a channel. If the
competing for access to limited system re-
channel is a bus, only an input is allowed
sources such as memory, CPU, or network
at a time. When N light beams are com-
bandwidth.
bined with an optical element, only 1/N of
the power of each beam finds its way into the
fall time (1) in digital electronics, the pe-
combined beam. Large fan-in is quite im-
riod of duration of the transition of a digital
practical for VLSI, because it uses a unique
signal from a stable high-voltage level to a
discrete channel for each input and current
stable low-voltage level.
flows are limited by transistor capacitance.
(2) in optics, the time interval for the
falling edge of an optical pulse to transition fan-out (1) the limit to the number of load-
from 90% to 10% of the pulse amplitude. Al- ing inputs that can be reliably driven by a
ternatively, values of 80% and 20% may be driving device’s output.
used.
(2) multiple outputs of a bus. A signal
is distributed into multiple channels. With a
falling edge (1) the region of a waveform fan-out of N, each channel receives only 1/N
when the wave goes from its high state to its of the light power. Large fan-out is quite im-
low state. practical for VLSI, because it uses a unique
(2) the high-to-low transition in voltage of discrete channel for each output and current
a time-varying digital signal. flows are limited by transistor capacitance.

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2000 by CRC Press LLC