1 files changed, 28 insertions, 0 deletions
diff --git a/fpga/usrp2/sdr_lib/acc.v b/fpga/usrp2/sdr_lib/acc.v
new file mode 100644
index 000000000..a2da9c86d
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/acc.v
@@ -0,0 +1,28 @@
+
+module acc
+  #(parameter IWIDTH=16, OWIDTH=30)
+    (input clk,
+     input clear,
+     input acc,
+     input [IWIDTH-1:0] in,
+     output reg [OWIDTH-1:0] out);
+
+   wire [OWIDTH-1:0] in_signext;
+   sign_extend #(.bits_in(IWIDTH),.bits_out(OWIDTH)) 
+     acc_signext (.in(in),.out(in_signext));
+   
+   //  CLEAR & ~ACC  -->  clears the accumulator
+   //  CLEAR & ACC -->    loads the accumulator
+   //  ~CLEAR & ACC -->   accumulates
+   //  ~CLEAR & ~ACC -->  hold
+   
+   wire [OWIDTH-1:0] addend1 = clear ? 0 : out;
+   wire [OWIDTH-1:0] addend2 = ~acc ? 0 : in_signext;
+   wire [OWIDTH-1:0] sum_int = addend1 + addend2;
+
+   always @(posedge clk)
+     out <= sum_int;
+   
+endmodule // acc
+
+