,
-
.I
-
’
-
Model
5340A
Theory of Operation
4
-
7.
5340A INTEGRATED
CIRCUITS
-
THEORY
OF
OPERATION
4
-
8.
The
5340A
uses
70
different types of integrated circuits. Twenty
-
two of these are basic logic
gates described in Paragraph
4
-
3.
The following paragraphs describe the integrated circuits used
in the
5340A
other than the basic logic types.
4
-
9.
256
-
Bit
Read
-
Only
-
Memories
1816
-
0003,1816
-
0004,1816
-
0184,
and
1816
-
0185
4
-
10.
A
read
-
only
-
memory
is
a
device that allows storage of pre
-
programmed data for later
retrieval. The
1816
series
of
ROM’s
are 16
-
pin dual in
-
line
IC’s
that allow eight different bits
to be stored for each
of
the
32
addresses. The five input lines give rise to
25
=
32
possible combi
-
nations of input addresses. Figure
4
-
3
shows the pin connections for the
1816
series.
Figure
4
-
3.
Logic Diagram for
1816
-
0003, 1816
-
0004, 1816
-
0184,
and
1816
-
0185
ROM’s
INPUT
ADDRESSES
(15-4
ENABLE
BO
I--
1
I
lo
11
I:T
84
B3
I:
EIGHT
-
BIT
’
WORD
OUTPUT
4
-
11.
One use of
ROM’s
is
in calculators where they are used to store conversion information or
to perform transformation.
For example,
a
ROM
could be used to output (in binary) the equiv
-
alent Fahrenheit temperature for
a
given centrigrade temperature.
ROM’s
can also be used fok
other simple transforms. For example, assume
it
is
desired to solve the equation
Y
=
2
X
+1.
For any value of
X
(from
0
to
31),
a
ROM
could be pre
-
programmed to give the value of
Y
that
satisfies the above equation.
Table
4
-
1
lists
the data that would be pre
-
programmed for this
example.
4
-
3
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