19-bit fifo handling for receive side of eth/udp system

1 files changed, 42 insertions, 0 deletions

diff --git a/control_lib/newfifo/fifo19_rxrealign.v b/control_lib/newfifo/fifo19_rxrealign.v
new file mode 100644
index 000000000..35ad90951
--- /dev/null
+++ b/control_lib/newfifo/fifo19_rxrealign.v
@@ -0,0 +1,42 @@
+
+
+//  Adds a junk line at the beginning of every packet, which the
+//   following stages should ignore.  This gives us proper alignment due
+//   to the 14 byte ethernet header
+
+// Bit 18 -- odd length
+// Bit 17 -- eof
+// Bit 16 -- sof
+// Bit 15:0 -- data
+
+module fifo19_rxrealign
+  (input clk, input reset, input clear,
+   input [18:0] datain, input src_rdy_i, output dst_rdy_o,
+   output [18:0] dataout, output src_rdy_o, input dst_rdy_i);
+   
+   reg 	rxre_state;
+   localparam RXRE_DUMMY  = 0;
+   localparam RXRE_PKT 	  = 1;
+   
+   assign dataout[18] 	  = datain[18];
+   assign dataout[17] 	  = datain[17];
+   assign dataout[16] 	  = (rxre_state==RXRE_DUMMY) | (datain[17] & datain[16]);  // allows for passing error signal
+   assign dataout[15:0] = datain[15:0];
+   
+   always @(posedge clk)
+     if(reset | clear)
+       rxre_state <= RXRE_DUMMY;
+     else if(src_rdy_i & dst_rdy_i)
+       case(rxre_state)
+	 RXRE_DUMMY :
+	   rxre_state <= RXRE_PKT;
+	 RXRE_PKT :
+	   if(datain[17])   // if eof or error
+	     rxre_state <= RXRE_DUMMY;
+       endcase // case (rxre_state)
+
+   assign src_rdy_o 	 = src_rdy_i & dst_rdy_i;   // Send anytime both sides are ready
+   assign dst_rdy_o = src_rdy_i & dst_rdy_i & (rxre_state == RXRE_PKT);  // Only consume after the dummy
+   
+endmodule // fifo19_rxrealign
+