Merge remote branch 'origin/usrp_e_next' into usrp_e_next

1 files changed, 68 insertions, 0 deletions

diff --git a/fpga/usrp2/gpmc/gpmc_to_fifo_async.v b/fpga/usrp2/gpmc/gpmc_to_fifo_async.v
new file mode 100644
index 000000000..55c0cef50
--- /dev/null
+++ b/fpga/usrp2/gpmc/gpmc_to_fifo_async.v
@@ -0,0 +1,68 @@
+
+module gpmc_to_fifo_async
+  (input [15:0] EM_D, input [1:0] EM_NBE, input EM_NCS, input EM_NWE,
+
+   input fifo_clk, input fifo_rst, input clear,
+   output reg [17:0] data_o, output reg src_rdy_o, input dst_rdy_i,
+
+   input [15:0] frame_len, input [15:0] fifo_space, output reg fifo_ready,
+   output reg bus_error );
+
+   reg [15:0] counter;
+   // Synchronize the async control signals
+   reg [1:0] 	cs_del, we_del;
+   always @(posedge fifo_clk)
+     if(fifo_rst)
+       begin
+	  cs_del <= 2'b11;
+	  we_del <= 2'b11;
+       end
+     else
+       begin
+	  cs_del <= { cs_del[0], EM_NCS };
+	  we_del <= { we_del[0], EM_NWE };
+       end
+
+   wire do_write = (~cs_del[0] & (we_del == 2'b10));
+   wire first_write = (counter == 0);
+   wire last_write = ((counter+1) == frame_len);
+
+   always @(posedge fifo_clk)
+     if(do_write)
+       begin
+	  data_o[15:0] <= EM_D;
+	  data_o[16] <= first_write;
+	  data_o[17] <= last_write;
+	  //  no byte writes data_o[18] <= |EM_NBE;  // mark half full if either is not enabled  FIXME
+       end
+
+   always @(posedge fifo_clk)
+     if(fifo_rst | clear)
+       src_rdy_o <= 0;
+     else if(do_write)
+       src_rdy_o <= 1;
+     else
+       src_rdy_o <= 0;    // Assume it was taken
+
+   always @(posedge fifo_clk)
+     if(fifo_rst | clear)
+       counter <= 0;
+     else if(do_write)
+       if(last_write)
+	 counter <= 0;
+       else
+	 counter <= counter + 1;
+
+   always @(posedge fifo_clk)
+     if(fifo_rst | clear)
+       fifo_ready <= 0;
+     else
+       fifo_ready <= /* first_write & */ (fifo_space > 16'd1023);
+
+   always @(posedge fifo_clk)
+     if(fifo_rst | clear)
+       bus_error <= 0;
+     else if(src_rdy_o & ~dst_rdy_i)
+       bus_error <= 1;
+   
+endmodule // gpmc_to_fifo_async