From 78abd7d98a5dc42aeafa89ed29a3ab8a1f9475f4 Mon Sep 17 00:00:00 2001
From: Matt Ettus <matt@ettus.com>
Date: Thu, 11 Nov 2010 18:50:49 -0800
Subject: gray code address for emi

---
 usrp2/extramfifo/nobl_if.v | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'usrp2/extramfifo')

diff --git a/usrp2/extramfifo/nobl_if.v b/usrp2/extramfifo/nobl_if.v
index 7ff7eaa03..b5ebe9c6b 100644
--- a/usrp2/extramfifo/nobl_if.v
+++ b/usrp2/extramfifo/nobl_if.v
@@ -39,6 +39,12 @@ module nobl_if
    assign 	   RAM_LDn = 0;
    // ZBT/NoBL RAM actually manages its own output enables very well.
    assign 	   RAM_OEn = 0;
+
+   // gray code the address to reduce EMI
+   wire [DEPTH-1:0] address_gray;
+   
+   bin2gray #(.WIDTH(DEPTH)) bin2gray (.bin(address),.gray(address_gray));
+   
    
    //
    // Pipeline stage 1
@@ -62,7 +68,7 @@ module nobl_if
 	  
 	  if (enable)
 	    begin
-	       address_pipe1 <= address;
+	       address_pipe1 <= address_gray;
 	       write_pipe1 <= write;
 //	       RAM_WEn <= ~write;  // Creates IOB flop
 	       
-- 
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