elastic_cross_clock.v

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`timescale 1ns/1ps

module  elastic_cross_clock#(
    parameter WIDTH=2,          // width of the pulse counter
    parameter EXTRA_DLY=0)(     // 0 or 1 - output duty cycle control
    input              rst,
    input              src_clk,
    input              dst_clk,
    input              in_pulses,
    output             out_pulse,
    output             busy
);
    reg   [WIDTH-1:0] pend_cntr=0;
    wire              busy_single;
    wire              single_rq_w;

//    assign busy = busy_single && (|pend_cntr);
    assign busy = busy_single || (|pend_cntr);
    assign single_rq_w = !busy_single && ((|pend_cntr) || in_pulses);
    
    always @(posedge src_clk) begin
        if      (rst)                        pend_cntr <= 0;
        else if ( in_pulses && !single_rq_w) pend_cntr <= pend_cntr + 1;
        else if (!in_pulses &&  single_rq_w) pend_cntr <= pend_cntr - 1;
    end
    
    pulse_cross_clock #(
        .EXTRA_DLY(EXTRA_DLY)
    ) pulse_cross_clock_i (
        .rst       (rst), // input
        .src_clk   (src_clk), // input
        .dst_clk   (dst_clk), // input
        .in_pulse  (single_rq_w), // input
        .out_pulse (out_pulse), // output
        .busy      (busy_single) // output
    );
    
endmodule