| XC3000 | XC4000E | XC4000X | XC5200 | XC9000 | Spartan | SpartanXL | Virtex |
|---|---|---|---|---|---|---|---|
| Macro | Macro | Macro | Macro | Macro | Macro | Macro | 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, XC4000, XC5200, XC9000, Spartans |  |
