Libraries GuideChapter 11: Design Elements (X74_42 to X74_521)
X74_139
2- to 4-Line Decoder/Demultiplexer with Active-Low Outputs and Active-Low Enable
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| N/A
| N/A
|
X74_139 implements one half of a standard 74139 dual 2- to 4-line decoder/demultiplexer. When the active-Low enable input (G) is Low, one of the four active-Low outputs (Y3 - Y0) is selected with the 2-bit binary address on the A and B address input lines. B is the High-order address bit. The non-selected outputs are High. Also, when G is High all outputs are High.
X74_139 can be used as a 4-output active-Low demultiplexer by tying the data input to G.
Inputs
| Outputs
|
|---|
G
| B
| A
| Y3
| Y2
| Y1
| Y0
|
|---|
0
| 0
| 0
| 1
| 1
| 1
| 0
|
0
| 0
| 1
| 1
| 1
| 0
| 1
|
0
| 1
| 0
| 1
| 0
| 1
| 1
|
0
| 1
| 1
| 0
| 1
| 1
| 1
|
1
| X
| X
| 1
| 1
| 1
| 1
|
Figure 11.5 X74_139 Implementation XC3000, XC4000E, XC4000X, XC5200, XC9000, Spartan, SpartanXL