Priority decoder
A priority decoder is used to convert the 1-of-n code into the dual code . The binary number appears at the outputs, which corresponds to the highest input number to which a 1 is applied. The value of the other inputs has no effect. The most significant bit is given priority , which is where the name comes from. Due to this property, the priority decoder can also be set up to decode a sum code in which the number of ones indicates the value.
Priority decoders are e.g. B. available as the following IC components :
| Type | designation | family |
|---|---|---|
| 1 out of 10 code | SN74147 | TTL |
| 1-out-of-8 code (expandable) |
SN74148 | |
| MC10165 | ECL | |
| MC14532 | CMOS |
| value | entrance | output | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| J | x 9 | x 8 | x 7 | x 6 | x 5 | x 4 | x 3 | x 2 | x 1 | y 3 | y 2 | y 1 | y 0 | ||
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ||
| 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | ||
| 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | x | 0 | 0 | 1 | 0 | ||
| 3 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | x | x | 0 | 0 | 1 | 1 | ||
| 4th | 0 | 0 | 0 | 0 | 0 | 1 | x | x | x | 0 | 1 | 0 | 0 | ||
| 5 | 0 | 0 | 0 | 0 | 1 | x | x | x | x | 0 | 1 | 0 | 1 | ||
| 6th | 0 | 0 | 0 | 1 | x | x | x | x | x | 0 | 1 | 1 | 0 | ||
| 7th | 0 | 0 | 1 | x | x | x | x | x | x | 0 | 1 | 1 | 1 | ||
| 8th | 0 | 1 | x | x | x | x | x | x | x | 1 | 0 | 0 | 0 | ||
| 9 | 1 | x | x | x | x | x | x | x | x | 1 | 0 | 0 | 1 | ||