One primitive is available for the carrylookahead8 which containsonly carry look-ahead multiplexers. The following functions are pushed into the LUTS: SUM XOR, CIN multiplexers, and Carry propagation multiplexers.
Figure 1. Carry Look-Ahead Logic Primitive
Attributes
| Attribute | Description | Values |
|---|---|---|
| LOOKB | If TRUE, enable LOOKAHEAD to bring carry results from last stage. | TRUE or FALSE |
| LOOKD | If TRUE, enable LOOKAHEAD to bring carry results from last stage. | TRUE or FALSE |
| LOOKF | If TRUE, enable LOOKAHEAD to bring carry results from last stage. | TRUE or FALSE |
| LOOKH | If TRUE, enable LOOKAHEAD to bring carry results from last stage. | TRUE or FALSE |
Port Descriptions
| Port | Type | Description |
|---|---|---|
| COUTB | Output | Output of CLA multiplexer. |
| COUTD | Output | Output of CLA multiplexer. |
| COUTF | Output | Output of CLA multiplexer. |
| COUTH | Output | Output of CLA multiplexer. |
| CYA | Input | Input of CLA multiplexer. |
| CYB | Input | Input of CLA multiplexer. |
| CYC | Input | Input of CLA multiplexer. |
| CYD | Input | Input of CLA multiplexer. |
| CYE | Input | Input of CLA multiplexer. |
| CYF | Input | Input of CLA multiplexer. |
| CYG | Input | Input of CLA multiplexer. |
| CYH | Input | Input of CLA multiplexer. |
| PROPA | Input | Input of CLA multiplexer. |
| PROPB | Input | Input of CLA multiplexer. |
| PROPC | Input | Input of CLA multiplexer. |
| PROPD | Input | Input of CLA multiplexer. |
| PROPE | Input | Input of CLA multiplexer. |
| PROPF | Input | Input of CLA multiplexer. |
| PROPG | Input | Input of CLA multiplexer. |
| PROPH | Input | Input of CLA multiplexer. |
| CIN | Input | Input of CLA multiplexer. |