dsp_engine: don't use SD rounding in 8 bit mode, so we can have a flat noise floor.

1 files changed, 3 insertions, 2 deletions

diff --git a/usrp2/sdr_lib/round_sd.v b/usrp2/sdr_lib/round_sd.v
index aeeb3502f..94584f6ef 100644
--- a/usrp2/sdr_lib/round_sd.v
+++ b/usrp2/sdr_lib/round_sd.v
@@ -2,7 +2,8 @@
 
 module round_sd
   #(parameter WIDTH_IN=18,
-    parameter WIDTH_OUT=16)
+    parameter WIDTH_OUT=16,
+    parameter DISABLE_SD=0)
    (input clk, input reset,
     input [WIDTH_IN-1:0] in, input strobe_in,
     output [WIDTH_OUT-1:0] out, output strobe_out);
@@ -15,7 +16,7 @@ module round_sd
    sign_extend #(.bits_in(ERR_WIDTH),.bits_out(WIDTH_IN)) ext_err (.in(err), .out(err_ext));
    
    add2_and_clip_reg #(.WIDTH(WIDTH_IN)) add2_and_clip_reg
-     (.clk(clk), .rst(reset), .in1(in), .in2(err_ext), .strobe_in(strobe_in), .sum(sum), .strobe_out(strobe_out));
+     (.clk(clk), .rst(reset), .in1(in), .in2((DISABLE_SD == 0) ? err_ext : 0), .strobe_in(strobe_in), .sum(sum), .strobe_out(strobe_out));
    
    round #(.bits_in(WIDTH_IN),.bits_out(WIDTH_OUT)) round_sum (.in(sum), .out(out), .err(err));