MUXCY

2-to-1 Multiplexer for Carry Logic with General Output

MUXCY 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 MUXCY. The carry in (CI) input of an LC is connected to the CI input of the MUXCY. The select input (S) of the MUX is driven by the output of the lookup table (LUT) and configured as an XOR function. The carry out (O) of the MUXCY 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.

The variants, “MUXCY_D” and “MUXCY_L,” provide additional types of outputs that can be used by different timing models for more accurate pre-layout timing estimation.