National Semiconductor DM74184, DM74185A Technical data
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DM74184/DM74185A
BCD-to-Binary and Binary-to-BCD Converters
General Description
These monolithic converters are derived from the 256-bit
read only memories, DM5488, and DM7488. Emitter connections are made to provide direct read-out of converted
codes at outputs Y8 through Y1, as shown in the function
tables. These converters demonstrate the versatility of a
read only memory in that an unlimited number of reference
tables or conversion tables may be built into a system. Both
of these converters comprehend that the least significant
bits (LSB) of the binary and BCD codes are logically equal,
and in each case the LSB bypasses the converter as illustrated in the typical applications. This means that a 6-bit
converter is produced in each case. Both devices are cascadable to N bits.
An overriding enable input is provided on each converter
which when taken high inhibits the function, causing all outputs to go high. For this reason, and to minimize power
consumption, unused outputs Y7 and Y8 of the 185A and all
‘‘don’t care’’ conditions of the 184 are programmed high.
The outputs are of the open-collector type.
DM74184 BCD-TO-BINARY CONVERTERS
The 6-bit BCD-to-binary function of the DM74184 is analogous to the algorithm:
a. Shift BCD number right one bit and examine each dec-
ade. Subtract three from each 4-bit decade containing a
binary value greater than seven.
DM74184/DM74185A BCD-to-Binary and Binary-to-BCD Converters
June 1989
b. Shift right, examine, and correct after each shift until the
least significant decade contains a number smaller than
eight and all other converted decades contain zeros.
In addition to BCD-to-binary conversion, the DM74184 is
programmed to generate BCD 9’s complement or BCD 10’s
complement. Again, in each case, one bit of the complement code is logically equal to one of the BCD bits; therefore, these complements can be produced on three lines.
As outputs Y6, Y7 and Y8 are not required in the BCD-to-binary conversion, they are utilized to provide these complement codes as specified in the function table when the devices are connected as shown.
DM74185A BINARY-TO-BCD CONVERTERS
The function performed by these 6-bit binary-to-BCD converters is analogous to the algorithm:
a. Examine the three most significant bits. If the sum is
greater than four, add three and shift left one bit.
b. Examine each BCD decade. If the sum is greater than
four, add three and shift left one bit.
c. Repeat step b until the least-significant binary bit is in the
least-significant BCD location.
(Continued)
Connection Diagram
Order Number DM74184N or DM74185AN
See NS Package Number N16E
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.
TL/F/6561
TL/F/6561– 1
Absolute Maximum Ratings (Note)
Note:
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Voltage 7V
Input Voltage 5.5V
Output Voltage 7V
Operating Free Air Temperature
Range 0
Storage Temperature Range
Ctoa70§C
§
b
65§Ctoa150§C
The ‘‘Absolute Maximum Ratings’’ are those values
beyond which the safety of the device cannot be guaranteed. The device should not be operated at these limits. The
parametric values defined in the ‘‘Electrical Characteristics’’
table are not guaranteed at the absolute maximum ratings.
The ‘‘Recommended Operating Conditions’’ table will define
the conditions for actual device operation.
Recommended Operating Conditions
Symbol Parameter Min Nom Max Units
V
CC
V
IH
V
IL
V
OH
I
OL
T
A
Supply Voltage 4.75 5 5.25 V
High Level Input Voltage 2 V
Low Level Input Voltage 0.8 V
High Level Output Voltage 5.5 V
Low Level Output Current 12 mA
Free Air Operating Temperature 0 70
’184 and ’185A Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol Parameter Conditions Min
e
e
Max, V
e
Min, V
e
e
e
e
e
Min, I
Min, V
Min, I
Max, V
Max, V
Max, V
Max
Max
eb
12 mA
I
e
5.5V
O
e
Min
IH
e
Max
OL
e
Max
IL
e
5.5V
I
e
2.4V 25 mA
I
e
0.4V
I
V
I
I
CEX
V
OL
I
I
I
IH
I
IL
I
CCH
I
CCL
Input Clamp Voltage V
High Level Output V
Current V
Low Level Output V
Voltage V
Input Current@Max V
Input Voltage
High Level Input Current V
Low Level Input Current V
Supply Current with V
Outputs High
Supply Current with V
Outputs Low
CC
CC
IL
CC
IH
CC
CC
CC
CC
CC
e
e
Typ
(Note 1)
Max Units
b
1.5 V
100 mA
0.4 V
1mA
b
1mA
65 95 mA
80 99 mA
C
§
’184 and ’185A Switching Characteristics
e
at V
CC
5V and T
Symbol Parameter To (Output)
t
PLH
t
PHL
t
PLH
t
PHL
Note 1: All typicals are at V
e
25§C (See Section 1 for Test Waveforms and Output Load)
A
From (Input)
Propagation Delay Time Enable G
Low to High Level Output to Output
Propagation Delay Time Enable G
High to Low Level Output to Output
Propagation Delay Time Binary Select
Low to High Level Output to Output
Propagation Delay Time Binary Select
High to Low Level Output to Output
e
e
5V, T
CC
25§C.
A
2
e
400X,R
R
L1
e
15 pF (See Test Circuit)
C
L
e
L2
Min Max
600X
Units
35 ns
35 ns
35 ns
35 ns
General Description (Continued)
TABLE I. Package Count and Delay Times
Input Packages Total Delay Times (ns)
(Decades) Required
2 2 56 80
3 6 140 200
4 12 196 280
5 19 280 400
6 28 364 520
DM74184 BCD-to-Binary
for BCD-to-Binary Conversion
Typ Max
6-Bit Converter
BCD 9’s
Complement Converter
TL/F/6561– 2
DM74185A Binary-to-BCD
TABLE II. Package Count and Delay Times
for Binary-to-BCD Conversion
Input Packages Total Delay Times (ns)
(Bits) Required
Typ Max
4to6 1 25 40
7or8 3 50 80
9 4 75 120
10 6 100 160
11 7 125 200
12 8 125 200
13 10 150 240
14 12 175 280
15 14 175 280
16 16 200 320
17 19 225 360
18 21 225 360
19 24 250 400
20 27 275 440
TL/F/6561– 3
BCD’s 10’s
Complement Converter
TL/F/6561– 4
6-Bit Converter
TL/F/6561– 5
3
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