counter: Add "count_enable" pin

1 files changed, 6 insertions, 2 deletions

diff --git a/nandgame/counter.sv b/nandgame/counter.sv
index 2089194..87ecdd7 100644
--- a/nandgame/counter.sv
+++ b/nandgame/counter.sv
@@ -1,11 +1,12 @@
 // nandgame counter
+// counts on *falling* edge
 
 `timescale 1us/1us
 
 `ifndef NANDGAME_COUNTER
 `define NANDGAME_COUNTER
 
-module  counter #(
+module counter #(
   parameter DATA_WIDTH = 16
 ) (
   // input / value to store in counter
@@ -14,6 +15,9 @@ module  counter #(
   input wire st_store_X_in,
   // clock
   input wire clk_in,
+  // active high, whether to count
+  // st_store_X_in overrides this in any case.
+  input wire count_enable_in,
 
   // counter value
   output wire [(DATA_WIDTH-1):0] counter_out
@@ -45,7 +49,7 @@ end
 always @(negedge clk_in) begin
   if (st_store_X_in)
     counter_int <= X_in;
-  else
+  else if (count_enable_in)
     counter_int <= counter_int + 1;
 end