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Inputs B, C, and D switching
in respect to a BCD code.
Inputs A, B, and D low.
APPLICATIONS INFORMATION
Expanded decoding can be performed by using the
MC14028B and other CMOS Integrated Circuits. The
circuit in Figure 2 converts any 4−bit code to a decimal or
hexadecimal code. The accompanying table shows the input
binary combinations, the associated "output numbers" that
go "high" when selected, and the "redefined output
numbers" needed for the proper code. For example: For the
combination DCBA = 0111 the output number 7 is redefined
for the 4−bit binary, 4−bit gray, excess−3, or excess−3 gray
codes as 7, 5, 4, or 2, respectively. Figure 3 shows a 6−bit
binary 1−of−64 decoder using nine MC14028B circuits and
two MC14069UB inverters.
The MC14028B can be used in decimal digit displays,
such as, neon readouts or incandescent projection indicators
as shown in Figure 4.
20 ns
90%
INPUT A
50%
10%
20 ns
90%
INPUT C
10%
t
PLH
90%
Q4
10%
t
Figure 1. Dynamic Signal Waveforms
A
B
C
D
LOGIC DIAGRAM
http://onsemi.com
MC14028B
20 ns
V
DD
V
SS
1/f
20 ns
V
DD
50%
V
SS
t
PHL
V
OH
50%
V
OL
t
TLH
THL
D
C
MC14028B
Q9
15
Figure 2. Code Conversion Circuit and Truth Table
4
All outputs connected to respective
C
loads. f in respect to a system clock.
L
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
INPUTS
D
C
B
B
A
D
C
B
MC14028B
Q0
Q9
−8
15
OUTPUT NUMBERS
A
A
Q0
−0
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