added code to implement FORWARD_LATENCY using srl16

diff --git a/src/edu/berkeley/fleet/fpga/verilog/Verilog.java b/src/edu/berkeley/fleet/fpga/verilog/Verilog.java
index 1393c55..f0a25d4 100644 (file)
--- a/src/edu/berkeley/fleet/fpga/verilog/Verilog.java
+++ b/src/edu/berkeley/fleet/fpga/verilog/Verilog.java
@@ -42,6 +42,10 @@ import static edu.berkeley.fleet.two.FleetTwoFleet.*;
  */
 public class Verilog {
 
+    //public static final int FORWARD_LATENCY = 1;
+    public static final int FORWARD_LATENCY = 6;
+    public static final int REVERSE_LATENCY = 3;
+
     public static interface Value {
         public String  getVerilog();
         public Value   getBits(int high, int low);
@@ -566,7 +570,23 @@ public class Verilog {
             public String getAssignments() {
                 StringBuffer sb = new StringBuffer();
                 if (external) {
-                    sb.append("assign " +                  name +"_r_ = " + name + "_r;\n");
+                    int a = FORWARD_LATENCY - 1;
+                    if (a<0 || a>16) {
+                        throw new RuntimeException("cannot offer latency of " + FORWARD_LATENCY +"-1");
+                    } else if (a==0) {
+                        sb.append("assign " +                  name +"_r_ = " + name + "_r;\n");
+                    } else {
+                        a = a-1;  // CLK-to-Q gives us one cycle of latency anyways
+                        sb.append("SRL16E srl16_"+name+"_r\n");
+                        sb.append("              (.Q ("+name+"_r_),\n");
+                        sb.append("               .A0 ("+((a & (1<<0)) == 0 ? 0 : 1)+"),\n");
+                        sb.append("               .A1 ("+((a & (1<<1)) == 0 ? 0 : 1)+"),\n");
+                        sb.append("               .A2 ("+((a & (1<<2)) == 0 ? 0 : 1)+"),\n");
+                        sb.append("               .A3 ("+((a & (1<<3)) == 0 ? 0 : 1)+"),\n");
+                        sb.append("               .CE (1),\n");
+                        sb.append("               .CLK (clk),\n");
+                        sb.append("               .D ("+name+"_r));\n");
+                    }
                     sb.append("assign " +                  name +"_ = " + name + ";\n");
                 }
                 if (controlDriver != null) {