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X74_42

4- to 10-Line BCD-to-Decimal Decoder with Active-Low Outputs

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Virtex
Macro
Macro
Macro
Macro
Macro
Macro
Macro
N/A

figures/x4162n.gif

X74_42 decodes the 4-bit BCD number on the data inputs (A - D). Only one of the ten outputs (Y9 - Y0) is active (Low) at a time, which reflects the decimal equivalent of the BCD number on inputs A - D. All outputs are inactive (High) during any one of six illegal states, as shown in the truth table.

Inputs
Outputs
D
C
B
A
Selected (Low) Output
0
0
0
0
Y0
0
0
0
1
Y1
0
0
1
0
Y2
0
0
1
1
Y3
0
1
0
0
Y4
0
1
0
1
Y5
0
1
1
0
Y6
0
1
1
1
Y7
1
0
0
0
Y8
1
0
0
1
Y9
1
0
1
0
All Outputs High
1
0
1
1
All Outputs High
1
1
0
0
All Outputs High
1
1
0
1
All Outputs High
1
1
1
0
All Outputs High
1
1
1
1
All Outputs High
Selected output is Low (0) and all others are High

Figure 11.1 X74_42 Implementation XC3000, XC4000, XC5200, XC9000, Spartans

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