/*
    Building blocks for DFF based RAM compiler for SKY130 
    WORD        :   32-bit memory word with select and byte-level WE
    DEC6x64     :   6x64 Binary decoder
    SRAM64x32   :   Tri-state based 64x32 DFF RAM 
*/

module BYTE (
    input CLK,
    input WE,
    input SEL,
    input [7:0] Di,
    output [7:0] Do,
    input VPWR,
    input VGND
);

    wire [7:0]  q_wire;
    wire        we_wire;
    wire        SEL_B;
    wire        GCLK;

    sky130_fd_sc_hd__inv_1 INV( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .Y(SEL_B), .A(SEL));
    sky130_fd_sc_hd__and2_1 CGAND( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .A(SEL), .B(WE), .X(we_wire) );
    sky130_fd_sc_hd__dlclkp_1 CG( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .CLK(CLK), .GCLK(GCLK), .GATE(we_wire) );

    generate 
        genvar i;
        for(i=0; i<8; i=i+1) begin : BIT
            sky130_fd_sc_hd__dfxtp_1 FF ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .D(Di[i]), .Q(q_wire[i]), .CLK(GCLK) );
            sky130_fd_sc_hd__ebufn_2 OBUF ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .A(q_wire[i]), .Z(Do[i]), .TE_B(SEL_B) );
        end
    endgenerate 

endmodule


module WORD32 (
    input CLK,
    input [3:0] WE,
    input SEL,
    input [31:0] Di,
    output [31:0] Do,
    input VPWR,
    input VGND
);

    BYTE B0 ( .VPWR(VPWR), .VGND(VGND), .CLK(CLK), .WE(WE[0]), .SEL(SEL), .Di(Di[7:0]), .Do(Do[7:0]) );
    BYTE B1 ( .VPWR(VPWR), .VGND(VGND), .CLK(CLK), .WE(WE[1]), .SEL(SEL), .Di(Di[15:8]), .Do(Do[15:8]) );
    BYTE B2 ( .VPWR(VPWR), .VGND(VGND), .CLK(CLK), .WE(WE[2]), .SEL(SEL), .Di(Di[23:16]), .Do(Do[23:16]) );
    BYTE B3 ( .VPWR(VPWR), .VGND(VGND), .CLK(CLK), .WE(WE[3]), .SEL(SEL), .Di(Di[31:24]), .Do(Do[31:24]) );
    
endmodule 

module DEC2x4 (
    input           EN,
    input   [1:0]   A,
    output  [3:0]   SEL,
    input VPWR,
    input VGND
);
    sky130_fd_sc_hd__nor3b_2    AND0 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .Y(SEL[0]), .A(A[0]),   .B(A[1]), .C_N(EN) );
    sky130_fd_sc_hd__and3b_2    AND1 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[1]), .A_N(A[1]), .B(A[0]), .C(EN) );
    sky130_fd_sc_hd__and3b_2    AND2 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[2]), .A_N(A[0]), .B(A[1]), .C(EN) );
    sky130_fd_sc_hd__and3_2     AND3 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[3]), .A(A[1]),   .B(A[0]), .C(EN) );
    
endmodule

module DEC3x8 (
    input           EN,
    input [2:0]     A,
    output [7:0]    SEL,
    input VPWR,
    input VGND
);
    sky130_fd_sc_hd__nor4b_2   AND0  ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .Y(SEL[0])  , .A(A[0]), .B(A[1])  , .C(A[2]), .D_N(EN) ); // 000
    sky130_fd_sc_hd__and4bb_2   AND1 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[1])  , .A_N(A[2]), .B_N(A[1]), .C(A[0])  , .D(EN) ); // 001
    sky130_fd_sc_hd__and4bb_2   AND2 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[2])  , .A_N(A[2]), .B_N(A[0]), .C(A[1])  , .D(EN) ); // 010
    sky130_fd_sc_hd__and4b_2    AND3 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[3])  , .A_N(A[2]), .B(A[1]), .C(A[0])  , .D(EN) );   // 011
    sky130_fd_sc_hd__and4bb_2   AND4 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[4])  , .A_N(A[0]), .B_N(A[1]), .C(A[2])  , .D(EN) ); // 100
    sky130_fd_sc_hd__and4b_2    AND5 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[5])  , .A_N(A[1]), .B(A[0]), .C(A[2])  , .D(EN) );   // 101
    sky130_fd_sc_hd__and4b_2    AND6 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[6])  , .A_N(A[0]), .B(A[1]), .C(A[2])  , .D(EN) );   // 110
    sky130_fd_sc_hd__and4_2     AND7 ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(SEL[7])  , .A(A[0]), .B(A[1]), .C(A[2])  , .D(EN) ); // 111
endmodule


module DEC6x64 (
    input           EN,
    input   [5:0]   A,
    output  [63:0] SEL,
    input VPWR,
    input VGND
);
    wire [7:0] SEL0_w ;
    DEC3x8 DEC_L0 ( .VPWR(VPWR), .VGND(VGND), .EN(EN), .A(A[5:3]), .SEL(SEL0_w) );

    generate
        genvar i;
        for(i=0; i<8; i=i+1) begin : DEC_L1
            DEC3x8 U ( .VPWR(VPWR), .VGND(VGND), .EN(SEL0_w[i]), .A(A[2:0]), .SEL(SEL[7+8*i: 8*i]) );
        end
    endgenerate
endmodule

module MUX4x1_32(
    input   [31:0]      A0, A1, A2, A3,
    input   [1:0]       S,
    output  [31:0]      X,
    input VPWR,
    input VGND
);
    sky130_fd_sc_hd__mux4_1 MUX[31:0] ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .A0(A0), .A1(A1), .A2(A2), .A3(A3), .S0(S[0]), .S1(S[1]), .X(X) );
endmodule

module SRAM64x32(
    input CLK,
    input [3:0] WE,
    input EN,
    input [31:0] Di,
    output [31:0] Do,
    input [5:0] A,
    input VPWR,
    input VGND
);

    wire [63:0]     SEL;
    wire [31:0]     Do_pre;
    wire [31:0]     Di_buf;
    wire            CLK_buf;
    wire [3:0]      WE_buf;

    sky130_fd_sc_hd__clkbuf_16 CLKBUF ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(CLK_buf), .A(CLK));
    sky130_fd_sc_hd__clkbuf_16 WEBUF[3:0] ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(WE_buf), .A(WE));
    sky130_fd_sc_hd__clkbuf_16 DIBUF[31:0] ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .X(Di_buf), .A(Di));

    DEC6x64 DEC  ( .VPWR(VPWR), .VGND(VGND), .EN(EN), .A(A), .SEL(SEL) );

    generate
        genvar i;
        for (i=0; i< 64; i=i+1) begin : WORD
            WORD32 W ( .VPWR(VPWR), .VGND(VGND), .CLK(CLK_buf), .WE(WE_buf), .SEL(SEL[i]), .Di(Di_buf), .Do(Do_pre) );
        end
    endgenerate

    // Ensure that the Do_pre lines are not floating when EN = 0
    sky130_fd_sc_hd__ebufn_4 FLOATBUF[31:0] ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .A({32{EN}}), .Z(Do_pre), .TE_B({32{EN}}) );

    generate 
        //genvar i;
        for(i=0; i<32; i=i+1) begin : OUT
            sky130_fd_sc_hd__dfxtp_1 FF ( .VPWR(VPWR), .VGND(VGND), .VPB(VPWR), .VNB(VGND), .D(Do_pre[i]), .Q(Do[i]), .CLK(CLK) );
        end
    endgenerate 

endmodule