more sync progress. This is just a skeleton for now, with junk content

1 files changed, 56 insertions, 0 deletions

diff --git a/usrp2/gpmc/fifo_to_gpmc_sync.v b/usrp2/gpmc/fifo_to_gpmc_sync.v
new file mode 100644
index 000000000..647a507b4
--- /dev/null
+++ b/usrp2/gpmc/fifo_to_gpmc_sync.v
@@ -0,0 +1,56 @@
+
+// Assumes a GPMC cycle with GPMC clock, as in the timing diagrams
+//   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_sync
+  (input arst,
+   input [17:0] data_i, input src_rdy_i, output reg dst_rdy_o,
+   input EM_CLK, inout [15:0] EM_D, input EM_NCS, input EM_NOE,
+   output fifo_ready, 
+   output reg bus_error);
+   
+   reg [10:0] 	counter;
+   wire 	first_write = (counter == 0);
+   wire 	last_write = ((counter+1) == frame_len);
+   wire 	do_write = ~EM_NCS & ~EM_NWE;
+   
+   always @(posedge EM_CLK or posedge arst)
+     if(arst)
+       data_o <= 0;
+     else 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 EM_CLK or posedge arst)
+     if(arst)
+       src_rdy_o <= 0;
+     else if(do_write & ~bus_error)  // Don't put junk in if there is a bus error
+       src_rdy_o <= 1;
+     else
+       src_rdy_o <= 0;    // Assume it was taken, ignore dst_rdy_i
+
+   always @(posedge EM_CLK or posedge arst)
+     if(arst)
+       counter <= 0;
+     else if(do_write)
+       if(last_write)
+	 counter <= 0;
+       else
+	 counter <= counter + 1;
+
+   assign fifo_ready = first_write & (fifo_space > frame_len);
+   
+   always @(posedge EM_CLK or posedge arst)
+     if(arst)
+       bus_error <= 0;
+     else if(src_rdy_o & ~dst_rdy_i)
+       bus_error <= 1;
+   // must be reset to make the error go away
+
+endmodule // fifo_to_gpmc_sync