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RYBACK
A step-up transformer used in a
display
to provide the high
voltage.
GATE
f.
A circuit with one output that re-
sp-ends only when a certain combina-
tion of pulses is present at the
inputs.
2.
A circuit in which one signal
sWitches another signal on and off,
3. To control the passage of a pulse
or signal.
HARNESS
A prefabricated assembly of insulated
wires and terQ1inals ready to
be
at·
tached to a piece of equipment.
HEXADECIMAL
A number system using the equivalent
of the
de~imal
number 16 as a
base.
The symbols 0-9 and
A-
F are usually
used.
IMPLODE
To
burst
inward; the inward collapse of
a
vacuum
tube.
I/O
Input/Output.
mQ
IntemJpt request. IRQ is a control
sig-
nal to the microprocessor
th
at is gener-
ated by external logic. This signal tells
the microprocessor that external logic
needs attention. Depending on the
pro-
gram, the processor mayor may not
re-
spond.
LED
The abbreviation for a light-emitting
diode.
LOCKOur COIL
Directs coins. into the coin return bOx
when there is no power to the game.
LOGICSTA1E
The binary
(1
or 0) value at the node
of a logic element or integrated circuit
during a particular time. Also called the
logic leveL The list below shows the
voltage levels corresponding to the
log-
ic states (levels) in a TTL system.
Logic 0, Low
=
0 VDC to +0.8 VDC
Grey Area (Tri-State Level)
=
+0.8 VDC to +2.4 VDC
Logic 1, High
=
+2.4 VDC to +5 VDC
MULTIPLEXER
A
device that takes several low-speed
inpurs and combines them into one
high-speed data stream for simultane-
ous transmission on a single line.
gl-2
".
NMl
Non-maskable interrupt.
NMI
is a re-
quest for service by the microprocessor
from external logic. The microprocessor
cannot ignore this interrupt request.
PAGE
A subsection of memory. A read-only
memory device (see
ROM)
is broken
into discrete blocks of data. These
blocks are called
pages.
Each block has
X
number of bytes.
PCB
The abbreviation for a printed-circuit
board.
PHOTOTRANSISTOR
A transistor that is activated
by an
external
light source
..
P01ENI10METER
1.
A
r~sis[or
that has a
continuously moving
contact which is
gener-
ally mounted on a mov-
ing shaft. Used chiefly
as a voltage
divider.
Also called a pot
(slang).
2.
An
instrument for
me;J,Suring a voltage by
balancing it against a
known voltage.
RAM
Random-access
memo-
ry.
A device for the
tem-
porary storage of data.
RAS1ER-SCAN DISPL\.Y
A display system whereby im-
ages are displayed by contin-
uously scanning the
cathode-
ray tube horizontally and
vellically with an electron
beam.
The
display system controls the intensity of
the electron
beam.
RETRACE
In a raster-scan display, retrace is the
time during which the cathode-ray tube
electron beam is resetting either from
right to left or from bottom to
top.
RESISTOR
A device designed to have a definite
amount of resistance. Used in circuits to
limit current flow or to provide a
volt-
age drop.
ROM
Read-only memol)'. A device for the
permanent storage of
data
~
SIGNATIJRE ANALYSIS
i
A process of isolating digital logic faults
at the component level by means of
special test equipment called signature
analyzers. Basically, sigpature analyzers
(e.g., the ATARI® CAT Box) convert
lengthy bit streams into four-digit hex-
adecimal Signatures. The signature read
by the analyzer at each
circuit
node is
then compared with the known good
signature for that node. This process
continues until a fault is located.
mOUBLESHOOT
The process of locating and repairing a
fault.
VECTOR
A
line segment
drawn
between specific
X and Y coordinates
on
a cathode-ray
tube.
WATCHDOG
A counter circuit
designed to
protect
the
micropro-
cessor
from
self-destruction if a program
malfunc-
tion
occurs.
If a malfunction does oc-
cur, the counter applies continuous
pulses to the reset line of the micropro-
cessor, which
causes
the
microproces-
sor
to keep
resetting.
X-Y
DISPLAY
A display system whereby images are
d isplayed with vectors.
ZENER DIODE
A special diode used as a regulator. Its
main characteristic is breaking down at
a specified reverse-bias (Zener) voltage.
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