1 files changed, 62 insertions, 0 deletions
diff --git a/serdes/serdes_fc_rx.v b/serdes/serdes_fc_rx.v
new file mode 100644
index 000000000..4dd46e27f
--- /dev/null
+++ b/serdes/serdes_fc_rx.v
@@ -0,0 +1,62 @@
+
+
+module serdes_fc_rx
+  #(parameter LWMARK = 64,
+    parameter HWMARK = 320)
+    (input clk, input rst,
+     input [15:0] fifo_space, 
+     output reg send_xon,
+     output reg send_xoff,
+     input sent);
+    
+   reg [15:0] 	  countdown;
+   reg 		  send_xon_int, send_xoff_int;
+   
+   always @(posedge clk)
+     if(rst)
+       begin
+	  send_xon_int <= 0;
+	  send_xoff_int <= 0;
+	  countdown <= 0;
+       end
+     else 
+       begin
+	  send_xon_int <= 0;
+	  send_xoff_int <= 0;
+	  if(countdown == 0)
+	    if(fifo_space < LWMARK)
+	      begin
+		 send_xoff_int <= 1;
+		 countdown <= 240;
+	      end
+	    else
+	      ;
+	  else
+	    if(fifo_space > HWMARK)
+	      begin
+		 send_xon_int <= 1;
+		 countdown <= 0;
+	      end
+	    else
+	      countdown <= countdown - 1;
+       end // else: !if(rst)
+
+   // If we are between the high and low water marks, we let the countdown expire
+
+   always @(posedge clk)
+     if(rst)
+       send_xon <= 0;
+     else if(send_xon_int)
+       send_xon <= 1;
+     else if(sent)
+       send_xon <= 0;
+
+   always @(posedge clk)
+     if(rst)
+       send_xoff <= 0;
+     else if(send_xoff_int)
+       send_xoff <= 1;
+     else if(sent)
+       send_xoff <= 0;
+   
+endmodule // serdes_fc_rx