Add tests for Xilinx UG901 examples

tests/xilinx_ug901/rams_init_file.v

@@ -0,0 +1,24 @@
+// Initializing Block RAM from external data file
+// Binary data
+// File: rams_init_file.v 
+
+module rams_init_file (clk, we, addr, din, dout);
+input clk;
+input we;
+input [5:0] addr;
+input [31:0] din;
+output [31:0] dout;
+
+reg [31:0] ram [0:63];
+reg [31:0] dout;
+
+initial begin
+$readmemb("rams_init_file.data",ram);
+end
+
+always @(posedge clk)
+begin
+  if (we)
+     ram[addr] <= din;
+  dout <= ram[addr];
+end endmodule