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src_bsc_lib_RTL/SizedFIFO0.v

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+
+// Copyright (c) 2000-2012 Bluespec, Inc.
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+// $Revision$
+// $Date$
+
+`ifdef BSV_ASSIGNMENT_DELAY
+`else
+  `define BSV_ASSIGNMENT_DELAY
+`endif
+
+`ifdef BSV_POSITIVE_RESET
+  `define BSV_RESET_VALUE 1'b1
+  `define BSV_RESET_EDGE posedge
+`else
+  `define BSV_RESET_VALUE 1'b0
+  `define BSV_RESET_EDGE negedge
+`endif
+
+`ifdef BSV_ASYNC_RESET
+ `define BSV_ARESET_EDGE_META or `BSV_RESET_EDGE RST
+`else
+ `define BSV_ARESET_EDGE_META
+`endif
+
+
+// Depth N FIFO (N > 1)
+module SizedFIFO0(CLK, RST, ENQ, FULL_N, DEQ, EMPTY_N, CLR);
+   parameter p1depth = 2;
+   parameter p2cntr_width = 2; // log2(p1depth+1)
+   parameter guarded = 1;
+
+   localparam truedepth = (p1depth >= 2) ? p1depth : 2;
+
+   input     CLK;
+   input     RST;
+   input     CLR;
+   input     ENQ;
+   input     DEQ;
+   output    FULL_N;
+   output    EMPTY_N;
+
+   reg       not_full;
+   reg       not_empty;
+   reg [p2cntr_width-1 : 0] count;
+
+   assign                 EMPTY_N = not_empty;
+   assign                 FULL_N = not_full;
+
+`ifdef BSV_NO_INITIAL_BLOCKS
+`else // not BSV_NO_INITIAL_BLOCKS
+   // synopsys translate_off
+   initial
+     begin
+        count      = 0 ;
+        not_empty  = 1'b0;
+        not_full   = 1'b1;
+     end // initial begin
+   // synopsys translate_on
+`endif // BSV_NO_INITIAL_BLOCKS
+
+
+   always @(posedge CLK `BSV_ARESET_EDGE_META)
+     begin
+        if (RST == `BSV_RESET_VALUE)
+          begin
+             count <= `BSV_ASSIGNMENT_DELAY 0 ;
+             not_empty <= `BSV_ASSIGNMENT_DELAY 1'b0;
+             not_full <= `BSV_ASSIGNMENT_DELAY 1'b1;
+          end // if (RST == `BSV_RESET_VALUE)
+        else
+           begin
+              if (CLR)
+                begin
+                   count <= `BSV_ASSIGNMENT_DELAY 0 ;
+                   not_empty <= `BSV_ASSIGNMENT_DELAY 1'b0;
+                   not_full <= `BSV_ASSIGNMENT_DELAY 1'b1;
+                end // if (CLR)
+              else begin
+                 if (DEQ && ! ENQ && not_empty )
+                   begin
+                      not_full <= `BSV_ASSIGNMENT_DELAY 1'b1;
+                      not_empty <= `BSV_ASSIGNMENT_DELAY  count != 'b01  ;
+                      count <= `BSV_ASSIGNMENT_DELAY count - 1'b1 ;
+                   end // if (DEQ && ! ENQ && not_empty )
+                 else if (ENQ && ! DEQ && not_full )
+                   begin
+                      not_empty <= `BSV_ASSIGNMENT_DELAY 1'b1;
+                      not_full <= `BSV_ASSIGNMENT_DELAY count != (truedepth - 1) ;
+                      count <= `BSV_ASSIGNMENT_DELAY count + 1'b1 ;
+                   end // if (ENQ && ! DEQ && not_full )
+              end // else: !if(CLR)
+           end // else: !if(RST == `BSV_RESET_VALUE)
+     end // always @ (posedge CLK or `BSV_RESET_EDGE RST)
+
+      // synopsys translate_off
+   always@(posedge CLK)
+     begin: error_checks
+        reg deqerror, enqerror ;
+
+        deqerror =  0;
+        enqerror = 0;
+        if (RST == ! `BSV_RESET_VALUE)
+           begin
+              if ( ! EMPTY_N && DEQ )
+                begin
+                   deqerror = 1 ;
+                   $display( "Warning: SizedFIFO0: %m -- Dequeuing from empty fifo" ) ;
+                end
+              if ( ! FULL_N && ENQ && (!DEQ || guarded) )
+                begin
+                   enqerror =  1 ;
+                   $display( "Warning: SizedFIFO0: %m -- Enqueuing to a full fifo" ) ;
+                end
+           end // if (RST == ! `BSV_RESET_VALUE)
+     end // block: error_checks
+   // synopsys translate_on
+
+endmodule // SizedFIFO0