diff --git a/GPIO/iCE40/ring.v b/GPIO/iCE40/ring.v
index 4e4c830680ac0155259094d85eddec559f09119b..7fd665c891721decfdb1787a51a29a614bfbe945 100644
--- a/GPIO/iCE40/ring.v
+++ b/GPIO/iCE40/ring.v
@@ -2,7 +2,7 @@
 `default_nettype none
 
 module top (
-    input CLK_12MHZ,           // system clock
+    input CLK_12MHZ, // the iCEBreaker has an external 12MHz oscillator
     output P1A1,
     input P1A2,
 );