| XC3000 | XC4000E | XC4000X | XC5200 | XC9000 | Spartan | SpartanXL | Virtex |
|---|---|---|---|---|---|---|---|
| N/A | N/A | N/A | Primitive | N/A | N/A | N/A | N/A |
CY_MUX is used to implement a 1-bit high-speed carry propagate function. One such function can be implemented per logic cell (LC), for a total of 4-bits per configurable logic block (CLB). The direct input (DI) of an LC is connected to the DI input of the CY_MUX. The carry in (CI) input of an LC is connected to the CI input of the CY_MUX. The select input (S) of the CY_MUX is driven by the output of the lookup table (LUT) and configured as an XOR function. The carry out (CO) of the CY_MUX reflects the state of the selected input and implements the carry out function of each LC. When Low, S selects DI; when High, S selects CI.
| Inputs | Outputs | ||
|---|---|---|---|
| S | DI | CI | CO |
| 0 | 1 | X | 1 |
| 0 | 0 | X | 0 |
| 1 | X | 1 | 1 |
| 1 | X | 0 | 0 |
The following figure depicts the application of the CY_MUX for a 4-bit adder. Also shown are the associated FMAP symbols and the CY_INIT function.
Figure 4.53 CY_MUX 4-Bit Adder Schematic XC5200 |  |
