verilog/rtl/scan_cells.v

`define default_netname none

module buffer_cell (
    input wire in,
    output wire out
    );
    assign out = in;
endmodule

module and_cell (
    input wire a,
    input wire b,
    output wire out
    );

    assign out = a & b;
endmodule

module or_cell (
    input wire a,
    input wire b,
    output wire out
    );

    assign out = a | b;
endmodule

module xor_cell (
    input wire a,
    input wire b,
    output wire out
    );

    assign out = a ^ b;
endmodule

module nand_cell (
    input wire a,
    input wire b,
    output wire out
    );

    assign out = !(a&b);
endmodule

module not_cell (
    input wire in,
    output wire out
    );

    assign out = !in;
endmodule

module mux_cell (
    input wire a,
    input wire b,
    input wire sel,
    output wire out
    );

    assign out = sel ? b : a;
endmodule

module dff_cell (
    input wire clk,
    input wire d,
    output reg q,
    output wire notq
    );

    assign notq = !q;
    always @(posedge clk)
        q <= d;

endmodule

module dffsr_cell (
    input wire clk,
    input wire d,
    input wire s,
    input wire r,
    output reg q,
    output wire notq
    );

    assign notq = !q;

    always @(posedge clk or posedge s or posedge r) begin
        if (r)
            q <= '0;
        else if (s)
            q <= '1;
        else
            q <= d;
    end
endmodule

// for scan wrapper
module latch (GATE, D, Q);
   input  GATE, D;
   output Q;
   reg    Q;
   always @ (GATE or D)
      if (GATE)
         Q <= D;
endmodule

module scan_flop(CLK, D, SCD, SCE, Q);
    input CLK, D, SCD, SCE;
    output Q;
    reg Q;

    always @(posedge CLK)
        Q <= SCE ? SCD : D;
endmodule