First cut at passing data buffers around on GPMC bus

1 files changed, 88 insertions, 0 deletions

diff --git a/usrp2/gpmc/dbsm.v b/usrp2/gpmc/dbsm.v
new file mode 100644
index 000000000..0f27be46a
--- /dev/null
+++ b/usrp2/gpmc/dbsm.v
@@ -0,0 +1,88 @@
+
+module bsm
+  (input clk, input reset, input clear,
+   input write_done,
+   input read_done,
+   output readable,
+   output writeable);
+
+   reg 	  state;
+   localparam ST_WRITEABLE = 0;
+   localparam ST_READABLE = 1;
+   
+   always @(posedge clk)
+     if(reset | clear)
+       state <= ST_WRITEABLE;
+     else
+       case(state)
+	 ST_WRITEABLE :
+	   if(write_done)
+	     state <= ST_READABLE;
+	 ST_READABLE :
+	   if(read_done)
+	     state <= ST_WRITEABLE;
+       endcase // case (state)
+
+   assign readable = (state == ST_READABLE);
+   assign writeable = (state == ST_WRITEABLE);
+   
+endmodule // bsm
+
+module dbsm
+  (input clk, input reset, input clear,
+   output reg read_sel, output read_ready, input read_done,
+   output reg write_sel, output write_ready, input write_done);
+
+   localparam NUM_BUFS = 2;
+
+   wire       [NUM_BUFS-1:0] readable, writeable, read_done_buf, write_done_buf;
+   
+   // Two of these buffer state machines
+   genvar     i;
+   for(i=0;i<NUM_BUFS;i=i+1)
+     generate
+	bsm bsm(.clk(clk), .reset(reset), .clear(clear), 
+		.write_done((write_sel == i) & write_done), 
+		.read_done((read_sel == i) & read_done), 
+		.readable(readable[i]), .writeable(writeable[i]));
+     endgenerate
+   
+   reg 	 full;
+   
+   always @(posedge clk)
+     if(reset | clear)
+       begin
+	  write_sel <= 0;
+	  full <= 0;
+       end
+     else
+       if(write_done)
+	 if(writeable[write_sel]==(NUM_BUFS-1))
+	   begin
+	      write_sel <= 0;
+	      if(read_sel == 0)
+		full <= 1;
+	   end
+	 else
+	   begin
+	      write_sel <= write_sel + 1;
+	      if(read_sel == write_sel + 1)
+		full <= 1;
+	   end // else: !if(writeable[write_sel]==(NUM_BUFS-1))
+       else if(read_done)
+	 full <= 0;
+
+   always @(posedge clk)
+     if(reset | clear)
+       read_sel <= 0;
+     else
+       if(read_done)
+	 if(readable[read_sel]==(NUM_BUFS-1))
+	   read_sel <= 0;
+	 else
+	   read_sel <= read_sel + 1;
+          
+   assign write_ready = writeable[write_sel];
+   assign read_ready = readable[read_sel];
+
+endmodule // dbsm