hw/top_earlgrey/ip/ast/rtl/aon_osc.sv

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
//############################################################################
//
// *Name: aon_osc
// *Module Description: AON Clock Oscilator
//
//############################################################################
`timescale 1ns/1ps

module aon_osc #(
// synopsys translate_off
   parameter time AON_EN_RDLY = 10us,
   parameter time AON_EN_FDLY = 100ns
// synopsys translate_on
) (
   input aon_en_i,              // AON Source Clock Enable
   output logic aon_clk_o,      // AON Clock Output
   output logic aon_clk_en_o    // AON Clock Enable Output
);

// synopsys translate_off

// localparam real AON_CLK_PERIOD = 5000; // 5000ns (200Khz)
// TBD
// sped up to 200ns by default.
// There should be a DV hook here so that the test can choose the actual frequency
   localparam real AON_CLK_PERIOD = 200;

logic init_start, clk;

initial begin
   clk = 1'b0;
   $display("\nAON Clock Period: %0dns", AON_CLK_PERIOD);
   init_start = 1'b1; #1;
   init_start = 1'b0;
end

always begin
   #(AON_CLK_PERIOD/2) clk = ~clk;
end

assign aon_clk_o = clk;

always_ff @( init_start, posedge aon_en_i, negedge aon_en_i ) begin
    if ( init_start )
       aon_clk_en_o <= 1'b0;
    else if ( !init_start && aon_en_i )
       aon_clk_en_o <= #(AON_EN_RDLY) aon_en_i;
    else if ( !init_start && !aon_en_i )
       aon_clk_en_o <= #(AON_EN_FDLY) aon_en_i;
end

// synopsys translate_on

endmodule  // of aon_osc