path: root/rtl/_modexpng_recombinator_cell.v

module modexpng_recombinator_cell
(
    clk,
    ce, clr,
    din, dout
);

    //
    // Headers
    //
    `include "modexpng_parameters.vh"
    
    //
    // Ports
    //
    input                clk;
    input                ce;
    input                clr;
    input  [ MAC_W -1:0] din;
    output [WORD_W -1:0] dout;

    reg [WORD_W -2:0] z;
    reg [WORD_W   :0] y;
    reg [WORD_W +1:0] x;

    assign dout = x[WORD_W-1:0];
    
    wire [WORD_W -2:0] din_z = din[3*WORD_W -2 :2*WORD_W];  // [46:32]
    wire [WORD_W -1:0] din_y = din[2*WORD_W -1 :  WORD_W];  // [31:16]
    wire [WORD_W -1:0] din_x = din[  WORD_W -1 :       0];  // [15: 0]
    
    always @(posedge clk)
        //
        if (ce) begin
            z <= din_z;
            y <= clr ? {1'b0,  din_y} : {1'b0,  din_y} + {2'b00, z};
            x <= clr ? {2'b00, din_x} : {2'b00, din_x} + {1'b0,  y} + {WORD_NULL, x[WORD_EXT_W-1:WORD_W]};        
        end
    
endmodule