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Carry in/out to be the last input/output for chains to be preserved

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Eddie Hung 2019-05-30 01:23:36 -07:00
parent 8c58c728a7
commit fdfc18be91
4 changed files with 91 additions and 12 deletions
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4
techlibs/xilinx/cells_sim.v
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@ -173,8 +173,8 @@ module XORCY(output O, input CI, LI);
assign O = CI ^ LI;
endmodule
(* abc_box_id = 3, lib_whitebox *)
module CARRY4(output [3:0] CO, O, input CI, CYINIT, input [3:0] DI, S);
(* abc_box_id = 3, lib_whitebox, abc_carry *)
module CARRY4((* abc_carry_out *) output [3:0] CO, output [3:0] O, (* abc_carry_in *) input CI, input CYINIT, input [3:0] DI, S);
assign O = S ^ {CO[2:0], CI | CYINIT};
assign CO[0] = S[0] ? CI | CYINIT : DI[0];
assign CO[1] = S[1] ? CO[0] : DI[1];