diff --git a/src/main.c b/src/main.c
index 3b8367b..1c17f4f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -86,7 +86,9 @@ static const char *usb_strings[] = {
 static bool paused = true;
 void sys_tick_handler(void)
 {
-	// TODO: measure frequency
+	if (paused) return;
+	step6502();
+	gpio_toggle(GPIOC, GPIO13);
 }
 
 
@@ -200,13 +202,7 @@ int main(void)
 
 	reset6502();
 
-	while (1) {
+	while (1)
 		usbd_poll(usbd_dev);
-
-		if (!paused) {
-			step6502();
-			gpio_toggle(GPIOC, GPIO13);
-		}
-	}
 }