Libraries GuideChapter 11: Design Elements (X74_42 to X74_521)
X74_138
3- to 8-Line Decoder/Demultiplexer with Active-Low Outputs and Three Enables
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| N/A
| N/A
|
X74_138 is an expandable decoder/demultiplexer with one active-High enable input (G1), two active-Low enable inputs (G2A and G2B), and eight active-Low outputs (Y7 - Y0). When G1 is High and G2A and G2B are Low, one of the eight active-Low outputs is selected with a 3-bit binary address on address inputs A, B, and C. The non-selected outputs are High. When G1 is Low or when G2A or G2B is High, all outputs are High.
X74_138 can be used as an 8-output active-Low demultiplexer by tying the data input to one of the enable inputs.
Inputs
| Outputs
|
|---|
C
| B
| A
| G1
| G2A
| G2B
| Y7
| Y6
| Y5
| Y4
| Y3
| Y2
| Y1
| Y0
|
|---|
0
| 0
| 0
| 1
| 0
| 0
| 1
| 1
| 1
| 1
| 1
| 1
| 1
| 0
|
0
| 0
| 1
| 1
| 0
| 0
| 1
| 1
| 1
| 1
| 1
| 1
| 0
| 1
|
0
| 1
| 0
| 1
| 0
| 0
| 1
| 1
| 1
| 1
| 1
| 0
| 1
| 1
|
0
| 1
| 1
| 1
| 0
| 0
| 1
| 1
| 1
| 1
| 0
| 1
| 1
| 1
|
1
| 0
| 0
| 1
| 0
| 0
| 1
| 1
| 1
| 0
| 1
| 1
| 1
| 1
|
1
| 0
| 1
| 1
| 0
| 0
| 1
| 1
| 0
| 1
| 1
| 1
| 1
| 1
|
1
| 1
| 0
| 1
| 0
| 0
| 1
| 0
| 1
| 1
| 1
| 1
| 1
| 1
|
1
| 1
| 1
| 1
| 0
| 0
| 0
| 1
| 1
| 1
| 1
| 1
| 1
| 1
|
X
| X
| X
| 0
| X
| X
| 1
| 1
| 1
| 1
| 1
| 1
| 1
| 1
|
X
| X
| X
| X
| 1
| X
| 1
| 1
| 1
| 1
| 1
| 1
| 1
| 1
|
X
| X
| X
| X
| X
| 1
| 1
| 1
| 1
| 1
| 1
| 1
| 1
| 1
|
Figure 11.4 X74_138 Implementation XC3000, XC4000E, XC4000X, XC5200, XC9000, Spartan, SpartanXL