Squashed B200 FPGA Source. Code from Josh Blum, Ian Buckley, and Matt Ettus.

Original-commit: 0df4b801a34697f2058b4a7b95e08d2a0576c9db

lib/fifo/monitor_axi_fifo.v

@@ -0,0 +1,123 @@
+//
+// Copyright 2012 Ettus Research LLC
+//
+
+
+//
+// This module is instantiated in parallel with a FIFO with AXI4-STREAM interfaces.
+// It tracks how many complete packets are contained within the FIFO, and also indicates
+// when the first word of a packet is presented on the FIFO outputs.
+//
+
+ 
+module monitor_axi_fifo
+  #(
+    parameter COUNT_BITS=8
+    )
+  (
+   input clk,
+   input reset,
+   input clear,
+   // Monitored FIFO signals
+   input i_tvalid,
+   input i_tready,
+   input i_tlast,
+   input o_tvalid,
+   input o_tready,
+   input o_tlast,
+   // FIFO status outputs
+   output reg [COUNT_BITS-1:0] pkt_count, // Exact whole packet count
+   output pkt_present // Flags any whole packets present
+ 
+   );
+
+   localparam WAIT_SOF = 0;
+   localparam WAIT_EOF = 1;
+    
+   
+   reg        in_state, out_state;
+   reg        pause_tx;
+                
+   //
+   // Count packets arriving into large FIFO
+   //
+   always @(posedge clk)
+     if (reset | clear) begin
+        in_state <= WAIT_SOF;
+     end else
+       case(in_state)
+	 //
+	 // After RESET or the EOF of previous packet, the first cycle with
+	 // input valid and input ready asserted is the SOF.
+	 //
+         WAIT_SOF: 
+           if (i_tvalid && i_tready) begin
+              in_state <= WAIT_EOF;
+           end else begin
+              in_state <= WAIT_SOF;
+           end
+	 //
+	 // EOF is signalled by the assertion i_tlast whilst input valid and ready are asserted.
+	 //
+         WAIT_EOF: 
+           if (i_tlast && i_tvalid && i_tready) begin
+              in_state <= WAIT_SOF;
+           end else begin
+              in_state <= WAIT_EOF;
+           end
+       endcase // case(in_state)
+   
+
+
+   //
+   // Count packets leaving large FIFO
+   //
+   always @(posedge clk)
+     if (reset | clear) begin
+        out_state <= WAIT_SOF;
+     end else
+       case(out_state)
+	 //
+	 // After RESET or the EOF of previous packet, the first cycle with
+	 // output valid and output ready asserted is the SOF.
+	 //
+         WAIT_SOF: 
+           if (o_tvalid && o_tready) begin
+              out_state <= WAIT_EOF;
+           end else begin
+              out_state <= WAIT_SOF;
+           end
+	 //
+	 // EOF is signalled by o_tlast asserted whilst output valid and ready asserted.
+	 //
+         WAIT_EOF: 
+           if (o_tlast && o_tvalid && o_tready) begin
+              out_state <= WAIT_SOF;
+           end else begin
+              out_state <= WAIT_EOF;
+           end
+       endcase // case(in_state)
+   
+
+   //
+   // Count packets in FIFO.
+   // No protection on counter wrap, 
+   // unclear how to gracefully deal with it.
+   // Perhaps generate Error IRQ so that S/W could clean up?
+   // Configure so that the pkt_count is ample for the application.
+   //
+   always @(posedge clk)
+     if (reset | clear)
+       pkt_count <= 0;
+     else if (((out_state==WAIT_EOF) && o_tlast && o_tvalid && o_tready ) &&
+	      ((in_state==WAIT_EOF) && i_tlast && i_tvalid && i_tready))
+       pkt_count <= pkt_count;
+     else if ((out_state==WAIT_EOF) && o_tlast && o_tvalid && o_tready)
+       pkt_count <= pkt_count - 1;
+     else if ((in_state==WAIT_EOF)  && i_tlast && i_tvalid && i_tready)
+       pkt_count <= pkt_count + 1;
+
+   // Non-zero packet count indicates packet(s) present.
+   assign pkt_present = |pkt_count;
+ 
+endmodule // count_tx_packets