From 1c6fdd3468d9b46190ede88a9acde6f835f2b135 Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Thu, 16 Jun 2022 14:33:46 -0700
Subject: [PATCH] Introduce NMIs

---
 homebrew-tutorial/main.asm | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/homebrew-tutorial/main.asm b/homebrew-tutorial/main.asm
index dd6d71e..ff2af30 100644
--- a/homebrew-tutorial/main.asm
+++ b/homebrew-tutorial/main.asm
@@ -7,6 +7,10 @@
 
 .include "header.asm"
 
+.segment "ZEROPAGE"
+
+nmi_count:  .res 2
+
 .segment "CODE"
 
 VRAM_CHARS = $0000
@@ -93,10 +97,18 @@ start:
     lda #$0f
     sta INIDISP
 
-    lda #$01
+    lda #%10000001
     sta NMITIMEN
 
 mainloop:
+
+    lda nmi_count
+    nmi_check:
+        wai
+        cmp nmi_count
+        beq nmi_check
+
+
     lda JOY1L
     bit #JOYL_L
     beq down_not_pressed
@@ -117,6 +129,7 @@ busywait:
 
 nmi:
     bit RDNMI
+    inc nmi_count
 _rti:
     rti