From 92f059ab54c46153be4fb1a18cab00871fc30559 Mon Sep 17 00:00:00 2001
From: Nam Tran <thnam.me@gmail.com>
Date: Mon, 26 Oct 2020 22:45:17 -0500
Subject: [PATCH] use only top bits of the data to display

---
 tdc/rtl/top.v  | 9 ++++++---
 tdc/sim/top.cc | 9 ++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/tdc/rtl/top.v b/tdc/rtl/top.v
index cdf1a36..17aedb3 100644
--- a/tdc/rtl/top.v
+++ b/tdc/rtl/top.v
@@ -14,9 +14,12 @@ module top #(parameter WIDTH=24)(
    wire clk_100MHz;
    reg buf_led = 0;
    wire buf_ready;
-   wire [5:0] buf_data;
+   /* verilator lint_off UNUSED */
+   parameter TDC_COUNTER_WIDTH = 28;
+   wire [TDC_COUNTER_WIDTH-1:0] buf_data;
    assign o_readyN = ~buf_ready;
-   assign o_dataN = ~buf_data;
+   assign o_dataN = ~buf_data[TDC_COUNTER_WIDTH-1:TDC_COUNTER_WIDTH-6];
+   /* verilator lint_on UNUSED */
 
 /* verilator lint_off PINMISSING */
    clk_gen #(.DIVISION(26)) clk_gen0 (
@@ -25,7 +28,7 @@ module top #(parameter WIDTH=24)(
                       .i_clk            (i_clk));
 /* verilator lint_on PINMISSING */
 
-   tdc #(.COUNTER_WIDTH(6)) tdc0 (
+   tdc #(.COUNTER_WIDTH(TDC_COUNTER_WIDTH)) tdc0 (
             // Outputs
             .o_ready                    (buf_ready),
             .o_data                     (buf_data),
diff --git a/tdc/sim/top.cc b/tdc/sim/top.cc
index 3f87e3a..fca78c0 100644
--- a/tdc/sim/top.cc
+++ b/tdc/sim/top.cc
@@ -46,9 +46,12 @@ int main(int argc, char **argv) {
    for (int k = 0; k < 3; k++) 
       tick(++tickcount, tb, tfp);
 
-   tb->i_startN = 0;
-   tick(++tickcount, tb, tfp);
-   tb->i_startN = 1;
+   for (int i = 0; i < 1000; i++) {
+      tb->i_startN = 0;
+      tick(++tickcount, tb, tfp);
+      tb->i_startN = 1;
+      tick(++tickcount, tb, tfp);
+   }
 
    for (int k = 0; k < 15; k++) 
       tick(++tickcount, tb, tfp);