Merge remote branch 'origin/usrp_e_next' into usrp_e_next

1 files changed, 37 insertions, 0 deletions

diff --git a/fpga/usrp2/gpmc/fifo_to_gpmc_async.v b/fpga/usrp2/gpmc/fifo_to_gpmc_async.v
new file mode 100644
index 000000000..cf8b6e861
--- /dev/null
+++ b/fpga/usrp2/gpmc/fifo_to_gpmc_async.v
@@ -0,0 +1,37 @@
+
+// Assumes an asynchronous GPMC cycle
+//   If a packet bigger or smaller than we are told is sent, behavior is undefined.
+//   If dst_rdy_i is low when we get data, behavior is undefined and we signal bus error.
+//   If there is a bus error, we should be reset
+
+module fifo_to_gpmc_async
+  (input clk, input reset, input clear,
+   input [17:0] data_i, input src_rdy_i, output dst_rdy_o,
+   output [15:0] EM_D, input EM_NCS, input EM_NOE,
+   input [15:0] frame_len);
+
+   // Synchronize the async control signals
+   reg [2:0] 	cs_del, oe_del;
+   reg [15:0] 	counter;
+   
+   always @(posedge clk)
+     if(reset)
+       begin
+	  cs_del <= 3'b11;
+	  oe_del <= 3'b11;
+       end
+     else
+       begin
+	  cs_del <= { cs_del[1:0], EM_NCS };
+	  oe_del <= { oe_del[1:0], EM_NOE };
+       end
+
+   wire do_read = ( (~cs_del[1] | ~cs_del[2]) & (oe_del[1:0] == 2'b01));  // change output on trailing edge
+   wire first_read = (counter == 0);
+   wire last_read = ((counter+1) == frame_len);
+
+   assign EM_D = data_i[15:0];
+
+   assign dst_rdy_o = do_read;
+
+endmodule // fifo_to_gpmc_async