Priority encoder
The priority encoder is a switching network from digital technology with the function 1 from n . The encoder outputs the number of the active input that has the highest priority. There are several variants available on the market as ICs , mostly as TTL or CMOS modules, or their corresponding further developments. Encoders with eight or ten inputs, which can usually also be cascaded, are common.
| entrance | output | |||||
|---|---|---|---|---|---|---|
| X3 | X2 | X1 | X0 | Y2 | Y1 | Y0 |
| 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 0 | 0 | 0 | 1 | 0 | 0 | 1 |
| 0 | 0 | 1 | X | 0 | 1 | 0 |
| 0 | 1 | X | X | 0 | 1 | 1 |
| 1 | X | X | X | 1 | 0 | 0 |
Priority encoders are used, for example, in arbiters for data bus control or in interrupt circuits. There are also more highly integrated modules for both applications that take over the complete administration, but these still contain a priority encoder in the core.
Most priority encoders work with negative logic; h., at least that the inputs are active L are. An L signal therefore triggers the corresponding input.