Updated delay module. Added block RAM implementation

Author: pConst

delay.sv

@@ -4,7 +4,7 @@
 //------------------------------------------------------------------------------
 
 // INFO -------------------------------------------------------------------------
-// Static Delay for arbitrary signal
+// Static Delay for arbitrary signal, v2
 // Another equivalent names for this module:
 //          conveyor.sv
 //          synchronizer.sv
@@ -14,21 +14,26 @@
 //
 //
 // CAUTION: delay module is widely used for synchronizing signals across clock
-//   domains. To automatically exclude input data paths from timing analisys
-//   set_false_path SDC constraint is integrated into this module. Applicable
-//   only to Intel/Altera Quartus IDE. Xilinx users still should write the
-//   constraints manually
+//   domains. When synchronizing, please exclude input data paths from timing
+//   analisys manually by writing appropriate set_false_path SDC constraint
 //
+// Version 2 introduces "ALTERA_BLOCK_RAM" option to implement delays using
+//   block RAM. Quartus can make shifters on block RAM aautomatically
+//   using 'altshift_taps' internal module when "Auto Shift Register
+//   Replacement" option is ON
 
 
 /* --- INSTANTIATION TEMPLATE BEGIN ---
 
 delay #(
-    .LENGTH( 2 )
+    .LENGTH( 2 ),
+    .WIDTH( 1 ),
+    .TYPE( "CELLS" )
 ) S1 (
     .clk( clk ),
     .nrst( 1'b1 ),
     .ena( 1'b1 ),
+
     .in(  ),
     .out(  )
 );
@@ -37,45 +42,110 @@ delay #(
 
 
 module delay #( parameter
-  LENGTH = 2    // delay/synchronizer chain length
-                // default length for synchronizer chain is 2
+  LENGTH = 2,          // delay/synchronizer chain length
+  WIDTH = 1,           // signal width
+  TYPE = "CELLS",      // "ALTERA_BLOCK_RAM" infers block ram fifo
+                       //   all other values infer registers
+
+  CNTR_W = $clog2(LENGTH)
 )(
   input clk,
   input nrst,
   input ena,
-  input in,
-  output out
+
+  input [WIDTH-1:0] in,
+  output [WIDTH-1:0] out
 );
 
 generate
 
   if ( LENGTH == 0 ) begin
-    assign out = in;
+
+    assign out[WIDTH-1:0] = in[WIDTH-1:0];
+
   end else if( LENGTH == 1 ) begin
 
-    logic data = 0;
+    logic [WIDTH-1:0] data = '0;
     always_ff @(posedge clk) begin
-      if (~nrst) begin
-        data <= 0;
-      end else if (ena) begin
-        data <= in;
+      if( ~nrst ) begin
+        data[WIDTH-1:0] <= '0;
+      end else if( ena ) begin
+        data[WIDTH-1:0] <= in[WIDTH-1:0];
       end
     end
-    assign out = data;
+    assign out[WIDTH-1:0] = data[WIDTH-1:0];
 
   end else begin
+    if( TYPE=="ALTERA_BLOCK_RAM" && LENGTH>=4 ) begin
 
-    logic [LENGTH:1] data = 0;
-    always_ff @(posedge clk) begin
-      if (~nrst) begin
-        data[LENGTH:1] <= 0;
-      end else if (ena) begin
-        data[LENGTH:1] <= {data[LENGTH-1:1],in};
+      logic [CNTR_W-1:0] delay_cntr = '0;
+
+      logic fifo_output_ena;
+      assign fifo_output_ena = (delay_cntr[CNTR_W-1:0] == LENGTH);
+
+      always_ff @(posedge clk) begin
+        if( ~nrst ) begin
+          delay_cntr[CNTR_W-1:0] <= '0;
+        end else begin
+          if( ena && ~fifo_output_ena) begin
+            delay_cntr[CNTR_W-1:0] <= delay_cntr[CNTR_W-1:0] + 1'b1;
+          end
+        end
       end
-    end
-    assign out = data[LENGTH];
 
-  end // if
+      logic [WIDTH-1:0] fifo_out;
+      scfifo #(
+        .LPM_WIDTH( WIDTH ),
+        .LPM_NUMWORDS( LENGTH ),   // must be at least 4
+        .LPM_WIDTHU( CNTR_W ),
+        .LPM_SHOWAHEAD( "ON" ),
+        .UNDERFLOW_CHECKING( "ON" ),
+        .OVERFLOW_CHECKING( "ON" ),
+        .ALMOST_FULL_VALUE( 0 ),
+        .ALMOST_EMPTY_VALUE( 0 ),
+        .ENABLE_ECC( "FALSE" ),
+        .ALLOW_RWCYCLE_WHEN_FULL( "ON" ),
+        .USE_EAB( "ON" ),
+        .MAXIMIZE_SPEED( 5 ),
+        .DEVICE_FAMILY( "Cyclone V" )
+      ) internal_fifo (
+        .clock( clk ),
+        .aclr( 1'b0 ),
+        .sclr( ~nrst ),
+
+        .data( in[WIDTH-1:0] ),
+        .wrreq( ena ),
+        .rdreq( ena && fifo_output_ena ),
+
+        .q( fifo_out[WIDTH-1:0] ),
+        .empty(  ),
+        .full(  ),
+        .almost_full(  ),
+        .almost_empty(  ),
+        .usedw(  ),
+        .eccstatus(  )
+      );
+
+      assign out[WIDTH-1:0] = (fifo_output_ena)?(fifo_out[WIDTH-1:0]):('0);
+
+    end else begin
+
+      logic [LENGTH:1][WIDTH-1:0] data = '0;
+      always_ff @(posedge clk) begin
+        integer i;
+        if( ~nrst ) begin
+          data <= '0;
+        end else if( ena ) begin
+          for(i=LENGTH-1; i>0; i--) begin
+            data[i+1][WIDTH-1:0] <= data[i][WIDTH-1:0];
+          end
+          data[1][WIDTH-1:0] <= in[WIDTH-1:0];
+        end
+      end
+      assign out[WIDTH-1:0] = data[LENGTH][WIDTH-1:0];
+
+    end // if TYPE
+  end // if LENGTH
 
 endgenerate
 

delay_tb.sv

@@ -0,0 +1,120 @@
+//------------------------------------------------------------------------------
+// delay_tb.sv
+// Konstantin Pavlov, [email protected]
+//------------------------------------------------------------------------------
+
+// INFO ------------------------------------------------------------------------
+// testbench for delay_tb.sv module
+
+`timescale 1ns / 1ps
+
+module delay_tb();
+
+logic clk200;
+initial begin
+  #0 clk200 = 1'b1;
+  forever
+    #2.5 clk200 = ~clk200;
+end
+
+logic clk400;
+initial begin
+  #0 clk400 = 1'b1;
+  forever
+    #1.25 clk400 = ~clk400;
+end
+
+logic clk33;
+initial begin
+  #0 clk33 = 1'b1;
+  forever
+    #15.151 clk33 = ~clk33;
+end
+
+logic rst;
+initial begin
+  #0 rst = 1'b0;
+  #10.2 rst = 1'b1;
+  #5 rst = 1'b0;
+end
+
+logic nrst;
+assign nrst = ~rst;
+
+logic rst_once;
+initial begin
+  #0 rst_once = 1'b0;
+  #10.2 rst_once = 1'b1;
+  #5 rst_once = 1'b0;
+end
+
+logic nrst_once;
+assign nrst_once = ~rst_once;
+
+logic [31:0] DerivedClocks;
+clk_divider #(
+  .WIDTH( 32 )
+) cd1 (
+  .clk( clk200 ),
+  .nrst( nrst_once ),
+  .ena( 1'b1 ),
+  .out( DerivedClocks[31:0] )
+);
+
+logic [31:0] E_DerivedClocks;
+edge_detect ed1[31:0] (
+  .clk( {32{clk200}} ),
+  .nrst( {32{nrst_once}} ),
+  .in( DerivedClocks[31:0] ),
+  .rising( E_DerivedClocks[31:0] ),
+  .falling(  ),
+  .both(  )
+);
+
+logic [31:0] RandomNumber1;
+c_rand rng1 (
+  .clk( clk200 ),
+  .rst( 1'b0 ),
+  .reseed( rst_once ),
+  .seed_val( DerivedClocks[31:0] ^ (DerivedClocks[31:0] << 1) ),
+  .out( RandomNumber1[15:0] )
+);
+
+c_rand rng2 (
+  .clk( clk200 ),
+  .rst( 1'b0 ),
+  .reseed( rst_once ),
+  .seed_val( DerivedClocks[31:0] ^ (DerivedClocks[31:0] << 2) ),
+  .out( RandomNumber1[31:16] )
+);
+
+// Module under test ==========================================================
+
+delay #(
+    .LENGTH( 10 ),
+    .WIDTH( 8 )
+    //.TYPE( "CELLS" )
+) d1 (
+    .clk( clk200 ),
+    .nrst( ~E_DerivedClocks[8] ),
+    .ena( 1'b1 ),
+
+    .in( RandomNumber1[7:0] ),
+    .out(  )
+);
+
+delay #(
+    .LENGTH( 10 ),
+    .WIDTH( 8 ),
+    .TYPE( "ALTERA_BLOCK_RAM" )
+) d2 (
+    .clk( clk200 ),
+    .nrst( ~E_DerivedClocks[8] ),
+    .ena( 1'b1 ),
+
+    .in( RandomNumber1[7:0] ),
+    .out(  )
+);
+
+
+endmodule