Merge branch 'udp'

1 files changed, 38 insertions, 0 deletions

diff --git a/fpga/usrp1/models/ssram.v b/fpga/usrp1/models/ssram.v
new file mode 100644
index 000000000..fd7339970
--- /dev/null
+++ b/fpga/usrp1/models/ssram.v
@@ -0,0 +1,38 @@
+
+// Model of Pipelined [ZBT] Synchronous SRAM
+
+module ssram(clock,addr,data,wen,ce);
+   parameter addrbits = 19;
+   parameter depth = 524288;
+
+   input clock;
+   input [addrbits-1:0] addr;
+   inout [35:0] data;
+   input wen;
+   input ce;
+
+   reg [35:0] ram [0:depth-1];
+   
+   reg read_d1,read_d2;
+   reg write_d1,write_d2;
+   reg [addrbits-1:0] addr_d1,addr_d2;
+   
+   always @(posedge clock)
+     begin
+	read_d1 <= #1 ce & ~wen;
+	write_d1 <= #1 ce & wen;
+	addr_d1 <= #1 addr;
+	read_d2 <= #1 read_d1;
+	write_d2 <= #1 write_d1;
+	addr_d2 <= #1 addr_d1;
+	if(write_d2)
+	  ram[addr_d2] = data;
+     end // always @ (posedge clock)
+
+   data = (ce & read_d2) ? ram[addr_d2] : 36'bz;
+
+   always @(posedge clock)
+     if(~ce & (write_d2 | write_d1 | wen))
+       $display("$time ERROR:  RAM CE not asserted during write cycle");
+   
+endmodule // ssram