Libraries GuideChapter 11: Design Elements (X74_42 to X74_521)
X74_42
4- to 10-Line BCD-to-Decimal Decoder with Active-Low Outputs
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| N/A
| N/A
|
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, XC4000E, XC4000X, XC5200, XC9000, Spartan, SpartanXL