toy-sram/rtl/src/array/ra_lcb_ddr.v

// © IBM Corp. 2021
// Licensed under the Apache License, Version 2.0 (the "License"), as modified by the terms below; you may not use the files in this
// repository except in compliance with the License as modified.
// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
//
// Modified Terms:
//
//   1)	For the purpose of the patent license granted to you in Section 3 of the License, the "Work" hereby includes implementations of
//   the work of authorship in physical form.
//
// Unless required by applicable law or agreed to in writing, the reference design distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language
// governing permissions and limitations under the License.
//
// Brief explanation of modifications:
//
// Modification 1: This modification extends the patent license to an implementation of the Work in physical form – i.e.,
// it unambiguously permits a user to make and use the physical chip.


// Local Clock Buffer for arrays
// Generates sim or implementation logic, depending on GENMODE.
// el_sel is early/late select (first/second pulse of cycle)

`timescale 1 ns / 1 ns

`include "toysram.vh"

module  ra_lcb_ddr (

    clk,    // =clk2x for genmode=0
    reset,  // used for genmode=1? seems not; could kill strobe with it
    cfg,
    strobe,
    el_sel

);

 parameter GENMODE = `GENMODE;	        // 0=NoDelay, 1=Delay

   input  clk;
   input  reset;
   input [0:`LCBDDR_CONFIGWIDTH-1] cfg;
   output strobe;
   output el_sel;

   //generate
   //   if (GENMODE == 0)
         reg el_sel_q;
   //endgenerate

   wire clk_dly;
   wire o0;
   wire o1;
   wire clk_dly2;

// generate strobe
generate

  if (GENMODE == 0)
     assign strobe = !clk & !reset; // strobe is inverted clk2x
  else begin

   // generate a strobe for ddr - is late pulse a delay of this, or gen'd independently from clk??
   // clk -> [delay] -> * --------------------- * -- and ---
   //                   | -- [delay] --- inv ---|

   // first edge delay
   ra_delay d0 (
      .i(clk),
      .o(o0)
   );
   // remaining
   /*
   genvar i;
   for (i = 1; i < `MAX_PULSE_DELAYS-1; i = i + 1) begin : d1
      ra_delay (
         .i()
         .o()
      )
   end
   */
   // select tap based on cfg

   assign clk_dly = o0;

   // first width delay
   ra_delay w0 (
      .i(clk_dly),
      .o(o1)
   );

   // remaining
   // select tap based on cfg

   assign clk_dly2 = o1;

   // create strobe
   assign strobe = clk_dly & !clk_dly2;

  end

endgenerate

// generate el_sel
generate

   if (GENMODE == 0) begin
      always @ (posedge clk)
         if (reset)
            el_sel_q <= 1'b0;
         else
            el_sel_q <= !el_sel_q;
      assign el_sel = el_sel_q;
   end else begin

      // el_sel is delayed version of clk

   end

endgenerate

endmodule