Play Meter

Issue: 1978 June 30 - Vol 4 Num 12

D-TYPE
FLIP-FLOP
t = n
)..4
~
c
Figure 3
Ro
D
LO
LO
HI
HI
Q ~
.2.. D So
d ~
t = n
J
Q~
LO
LO
HI
HI
HI
~ CLK
Figure 4
LO
HI
LO
HI
Q
CLR
I
Hl 1
LO ~
PULSE
rL
t = n + 1
K CLK
LO -
HI -
LO -
HI LO
HI HI
Q
Q
I
I
t =- n ot = n
: + 1
NO CHANGE
LO
HI
HI
LO
HI
LO
LO
HI
I
HI
I
LO ~
PULSE
Truth Table valid only
when CLR is HI
?1o
The exclusive OR gate is used
extensively in video games . The truth
table of Figure 2E shows that the
exclusive OR gate has a H 1 output
when anyone but not both of the
inputs is a H 1 . If both inputs ar·e a LO
or a H1 the output is a LO .
Such circuits are used for a variety of
storage , counting and timing oper-
ations .
The two outputs o.LI,.flip flop are Q
and its complement Q . The state of
the Q or normal output tells you the
state of the flip flop . If Q is a 1 the flip
flop is set , if it is a 0 the flip flop is
reset .
Rip Aops
A flip flop is a digital logic device
used to store one bit of binary data . It
has two stable states , one repre-
senting a binary 0 . The flip flop is the
basic logic element used in sequential
logic circuits. The primary character-
istic of a sequential circuit is memory.
D-type flip flop
The D-type flip flop has two
inputs . The D input is where you
apply the bit to be stored . The C or
CLK controls the flip flop . It is used
- to determine whether the input data
CLK
F"JgUre 5
A SIMPLE COUNTER
CLK
QA
QB
~
QD
I
t = n:t = n+1
LO
LO
HI
HI
Truth Table valid only when
and R are both HI
0
J-K MASTER SLAVE
FLIP-FLOP
~ K
c
I
s 0
?1
~J
t = n + 1
Q
I
I
I
I
I
I
I
is recognized or ignored . If the CLK
line is Hi the data on D is stored and
present at the Q output. If C is Lo ,
the D data is ignored and the bit
stored previously is retained . As long
as the CLK input is Hi , the Q output
will follow the D input .
This operation of the D flip flop is
only valid as long as the Preset and
Clear control lines are Hi. A Lo on
the preset causes Q to go Hi and
remain there . A Lo on the clear line
causes Q to go Lo . The Q output will
be the complement of Q . The
present and clear inputs predominate
over all other inputs. (Figure Three) .
J-K flip flop
The J -K flip flop is really two flip
flops in one, where one FF feeds the
other. This arrangement is called a
masterslave flip flop . The master flip
flop is the input circuit where the
input signals are applied . The slave
flip flop in the J -K circuit provides the
output signals and the slave gets its
inputs from the master. A clock pulse
controls both master and slave flip
flops (Figure Four) .
If both the J and K inputs are Lo ,
the clock impulse will have no effect
on the outputs; they will remain in
their previous states. When the J and
the K inputs are at opposite logic
levels , regardless of which input is Hi
and which is Lo , the negative going
edge of the clock signal will transfer
the J input bit to the Q output and
the K bit to the""'O" output . In effect this
input configuration , both Hi, makes
the JK flip flop a divide by 2 counter .
As with the D type flip flop the clear
input must be a Hl. A Lo outear
forces and holds Q Lo and Q , its
complement, H1 .
Counters
There are a wide variety of
counters used in games today .
Basically a counter is noth ing more
than a series of flip flops . A four-bit
counter for instance would have four
JK flip flops in series . The input data
would be fed to the first CLK input
and the Q output of each stage acts
as the clock of each succeeding flip
flop stage . The J and K inputs are at
a H11evel which makes each flip flop
stage a divide by 2 counter . Only the
Q output of each of the four flip -flop
stages are used . Each output will be
one half the output frequency of the
preceding stage (Figure Five) .
There are many other more
complex logic circuits used in games.
A good TTL Data Book will show the
operation of each of the different
types that you may need to know .
The next article will deal these circuits
and some of the more complex
circuits from a troubleshooting stand-
point rather than how they operate .
Music Programming
.....__ By Pat MaHhews
On the Ranch
Back at the ranch , here I am again
with the creme de Ia creme . Rising to
the top and to th~ occasion (in that
order) is, I find , a trifle easier during
the summers. I've turned 26 and
don 't really feel a year older. But let's
get on with the business at hand
before these following tunes get any
older .
Runaway-Jefferson
Starship-
Grunt JB-11274
Some more "Earth" music from
the West Coast legends . Open
another bottle of Dom Perignon and
sip slowly while escaping into this
smooth and easy ballad which is
almost as exquisite as the liquid
refreshment. It has all the character-
istics of a Starship enterprise : Marty
Balin 's easily recognizable lead vocals
and the fluid guitar styling of Paul
Kantner . From "Miracles" to "Count
On Me" and now to "Runaway ," the'
progression is evident. But where to
now? "It's a runaway hit," he said
with tongue-in -cheek. (A-Pop) (A-
MOR)
We Really Must Believe in Magic-
Jack Clement- Elektra E-45474-B
You really have to check the label
to make sure this isn 't Gordon
Lightfoot. Sounding a lot like the
Canadian balladeer , Jack Clement
(who?) comes on strong with this
impressive debut disk . It's an easy
surrealistic tune with great vocals out
front and effective , if not unusual
female backing . Could do well.
(A-MOR) (B-Pop)
Got a Feeling- Patrick Juvet - Casa-
blanca NB 924 D
It 's light disco with a Mamas &
Papas "feel" to it. A fine horn and
string arrangement highlight the
song- it's certainly not the lyrical
content ("got a feelin ' that I won 't be
needin' you"). Juvet is a newcomer
to the Casablanca fold , who seems to
sign everybody and unfortunately ,
anybody . It's produced by Jacques
Morali who also does the Village
People ("Macho Man") and therefore
should do well in discos. (A-Disco)
Prove It AU Night- Bruce Springs-
teen - Columbia 3-10763
"How can I tell radio stations that
this is what Springsteen's been doing
for the last three years?" That quote
was made by a record promoter who
shall remain nameless . However
after another listen , I conclude it's a
typical macho exercise in music and
besides Bruce Springsteen's follow-
ing will like anything he does , this
being no exception . And of course , it
has been three-plus years since Mr .
Springsteen has blessed his following
with anything and even "Born To
Run" gets old . Get ready , Bruce is
out to "prove it" again! (A-Pop)
You Don't Love Me Anymore-
Eddie Rabbitt-Elektra E-45488-A
A love ballad and not the kickin'
country stylings one would expect
from Mr . Rabbitt (I find that hard to
type with a straight, let us say , key) .
It's one heck of a pretty tune and it's
all about a love lost as the title
implies. Eddie Rabbitt seems to be
following other country singers (Dolly
Parton , Ronnie Milsap , etc) in the
cross over brigade and should fare
well with this single . (A -C&W)
(C-Pop) (A-MOR)
This Year's Girl- Elvis Costello-
Columbia 3 -10762
It probably took me longer than
anyone else to realize this Briton with
the fifties haircut is for real. The days
of a cult following could soon be over
for Elvis (Jeez) with this catchy
bouncy rocker. There are definite
Beatles flavorings and in some parts
Costello sounds like the Dave Clark
(how refreshing) . With the right push
by Columbia it could go far . (B-Pop)
Stay- Jackson Browne - Asylum E-
45485-A
Culled from the super selling
"Runnin ' On Empty" live lp , Jackson
Browne seems to have another
"Crowd pleaser ," so to speak , with
this one . Complete with falsetto
voice , this medium tempo re-make
should zoom up the charts. Bear in
mind , that the single "Runnin ' On
Empty" was (and still is) Jackson's
biggest selling single since "Doctor
My Eyes" and that was many moons
ago. "Stay" is a nice sentimental
follow-up . (A-Pop)
Freeway Song- Vicki Sue Robin-
son - RCA JH 11280
"I guess you just have to be able to
relate to freeways to get into this
one ." That's what I was thinking to
myself before listening . Then as the
song progressed I found that it's not
about bumper-to-bumper traffic at
all . No , it's a beautiful love ballad that
simply relates being in love to being
"free ." It's sort of breezy with flowing
vocals by Ms . Robinson who certain-
ly "Turned the Beat Around" on this
one . (B-Pop) (A -R&B) (A-MOR)
WORTH A LISTEN
Cheatin'- Rubicon- 20th Century
Fox
Three Times A Lady - Commo-
dores - Motown
Who Turned You On-Wilson Pic-
kett - Big Three
Under The Boardwalk-Bear-RCA
This Magic Moment- Richie Furay -
Asylum
Flying Over America- Fresh Aire -
Atlantic
Anytime-Journey-Columbia

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