From 91c662e528d9052d6c6d0625e99bc5a5a866763a Mon Sep 17 00:00:00 2001
From: Andreas Olofsson <andreas@adapteva.com>
Date: Tue, 23 Feb 2016 15:42:55 -0500
Subject: [PATCH] Adding experimental fifo circuit -not debugged

---
 common/hdl/oh_fifo_generic.v | 113 +++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 common/hdl/oh_fifo_generic.v

diff --git a/common/hdl/oh_fifo_generic.v b/common/hdl/oh_fifo_generic.v
new file mode 100644
index 0000000..ae71553
--- /dev/null
+++ b/common/hdl/oh_fifo_generic.v
@@ -0,0 +1,113 @@
+module oh_fifo_generic
+   (/*AUTOARG*/
+   // Outputs
+   dout, empty, full, prog_full, rd_count, wr_count,
+   // Inputs
+   nreset, wr_clk, wr_en, din, rd_clk, rd_en
+   );
+
+   //#####################################################################
+   //# INTERFACE
+   //#####################################################################
+   
+   // parameters
+   parameter DW        = 104;            // FIFO width 
+   parameter DEPTH     = 1;              // FIFO depth (entries)         
+   parameter PROG_FULL = DEPTH/2;        // FIFO full threshold 
+   parameter AW        = $clog2(DEPTH);  // FIFO address width (for model)
+
+   // common reset
+   input           nreset;       // asynch active low reset
+
+   // fifo write
+   input           wr_clk;       // write clock   
+   input           wr_en;        // write enable
+   input  [DW-1:0] din;          // write data
+   
+   // fifo read
+   input           rd_clk;       // read clock   
+   input 	   rd_en;        // read enable
+   output [DW-1:0] dout;         // read data
+
+   // status
+   output          empty;        // fifo is empty
+   output          full;         // fifo is full
+   output 	   prog_full;    // fifo is "half empty"
+   output [AW-1:0] rd_count;// fifo count on rd side
+   output [AW-1:0] wr_count;// fifo count on wr side
+
+   //#####################################################################
+   //# BODY
+   //#####################################################################
+   
+   reg [AW-1:0]    wr_addr;
+   reg [AW-1:0]    rd_addr;
+   reg [AW-1:0]    rd_count;
+   reg [AW-1:0]    wr_count;
+
+   // fifo indicators
+   assign empty     = (rd_count[AW-1:0] == 'b0);
+   assign full      = (wr_count[AW-1:0] == DEPTH);
+   assign prog_full = (wr_count[AW-1:0] >= PROG_FULL);   
+
+   // write side state machine
+   always @ ( posedge wr_clk or negedge nreset) 
+     if(!nreset) 
+       begin	   
+          wr_addr[AW-1:0]   <= 'd0;
+	  wr_count[AW-1:0]  <= 'd0;
+       end 
+     else if(wr_en & rd_en_sync) 
+	  wr_addr[AW-1:0] <= wr_addr[AW-1:0] + 'd1;
+     else if(wr_en) 
+       begin
+	  wr_addr[AW-1:0] <= wr_addr[AW-1:0]  + 'd1;
+	  wr_count[AW-1:0]<= wr_count[AW-1:0] + 'd1;	
+       end
+     else if(rd_en_sync) 
+       wr_count[AW-1:0]<= wr_count[AW-1:0] - 'd1;	
+
+   // read side state machine
+   always @ ( posedge rd_clk or negedge nreset) 
+     if(!nreset) 
+       begin	   
+          rd_addr[AW-1:0]   <= 'd0;
+	  rd_count[AW-1:0]  <= 'd0;
+       end 
+     else if(rd_en & wr_en_sync) 
+       rd_addr[AW-1:0] <= rd_addr[AW-1:0] + 'd1;
+     else if(rd_en) 
+       begin
+	  rd_addr[AW-1:0] <= rd_addr[AW-1:0]  + 'd1;
+	  rd_count[AW-1:0] <= rd_count[AW-1:0] - 'd1;	
+       end
+     else if(wr_en_sync) 
+       rd_count[AW-1:0] <= rd_count[AW-1:0] + 'd1;	
+         
+   // clock domain synchronizers
+   oh_dsync wr_sync(.dout (wr_en_sync),
+		    .clk  (rd_clk),
+		    .din  (wr_en));
+   
+   oh_dsync rd_sync(.dout (rd_en_sync),
+		    .clk  (wr_clk),
+		    .din  (rd_en));
+   
+   // dual ported memory (1rd, 1 wr)
+   oh_memory_dp  #(.DW(DW),
+		   .AW(AW))
+   fifo_mem(// Outputs
+	    .rd_dout	(dout[DW-1:0]),
+	    // Inputs
+	    .wr_clk	(wr_clk),
+	    .wr_en	(wr_en),
+	    .wr_wem	({(DW){1'b1}}),
+	    .wr_addr	(wr_addr[AW-1:0]),
+	    .wr_din	(din[DW-1:0]),
+	    .rd_clk	(rd_clk),
+	    .rd_en	(rd_en),
+	    .rd_addr	(rd_addr[AW-1:0]));
+   
+endmodule // oh_fifo_generic
+		    
+