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Service
Model
8672A
8-69. Common Control Block
8-70. The Control
Block
is
used in
conjunction
with
an array
of
related symbols in order to group
common
logic lines. Figure
8-12
shows
how the
Control Block
is
usually represented. Figure
8-13
shows
a
quad
D-Type
flip-flop with
reset. This can
be
redrawn by combining what
is
shown
in Fig¬
ures
8-12
and
8-13 about
Contiguous Blocks and
Common Control Blocks. The
result
is
shown in
Figure
8-14. Note that
the
more complex
repre¬
sentation shown in Figure
8-13 might
be
used
when
the
flip-flops
are
functionally
scattered
around the schematic (not
used
as
a
quad
unit).
CONTROL
BLOCK
YARRAY
Figure 8-12. Common Control
Block
1
DEC in-
1
r*
i
n
r*
i/
9
LLULI\
———
DATA
^
DATA
^
nATA
12
DATA
13
[—
•—i
i
<
1
—
i—
i—
i—t.
>
1^
l-s
Rrr
rr
\
r
/
"
Dn
L>
R
FF
S
r
/
"
Dp
Lr
n
PF
n
r r
\
r
/"
Dp
u
Q
CC
n
rr
S
r
/
"
Dp
u
—
—
—
~1
s^
S,
•^
z
——1
2
3
7
6
10
11
15
14
RESET
CLOCK
DATA<
1,^
,
9
'>
r
4
5
12
13
R
>C
i
"" r
°c
FF
»c
FF
°c
FF
°c
FF
2
^3
7
s^6
10
sj1
15
sj4
Figure 8-14.
Quad
D-Type Latch (Combined)
8-71. Complex
Devices
Figures
8-15 through 8-17 show how the
basic
symbols
can be
combined in
vsirious
ways to
illus¬
trate the behavior
of fairly complex
devices.
8-72. Quad D-Type Latch. Refer
to Figure
8-15.
The
register
control block
is
used
to illustrate
a
quad
D-type latch.
There
is
a
common active-low
reset
(R),
and
a
common
edge-triggered
control
input (C).
Since
there
is
only
one dependency
re¬
lationship, the controlling
input
is
not numbered
and the controlled function
(D)
is
subscripted
with
a
C.
R
i
REG
r"
FF
FF
FF
FF
Figure 8-13.
Quad
D-Type
Latch
(Individual)
Figure 8-15.
Quad
D-Type
Latch Example
8-18
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