From bd9edb1309e8726f3737f258c423b056c999a5c8 Mon Sep 17 00:00:00 2001
From: Samuel Walker <swalker@piwalker.net>
Date: Thu, 20 Mar 2025 19:39:06 -0600
Subject: [PATCH] bcd conversion

---
 main.s | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 62 insertions(+), 9 deletions(-)

diff --git a/main.s b/main.s
index 62f7001..89ebbbe 100644
--- a/main.s
+++ b/main.s
@@ -5,7 +5,7 @@
     .byte $01, $00 ; mapper 0, vertical mirroring
 
 .segment "VECTORS"
-    .addr 0 ; nmi interrupt
+    .addr nmi ; nmi interrupt
     .addr reset ; reset interrupt
     .addr 0 ; external interrupt
 
@@ -13,12 +13,65 @@
 
 .segment "CODE"
 
-reset:
-    ldx #3
-    inx
-    inx
-    dex
+check:
+    cmp #5
+    bcc skip
+    clc
+    adc #3
+skip:
+    rts
 
-    ldy #7
-    dey
-    rts
\ No newline at end of file
+reset:
+    lda #173
+    sta $00
+    lda #0
+    sta $01
+    sta $02
+dabble:
+    ; check first digit
+    lda $01
+    and #$F
+    jsr check
+    sta $03
+    lda #$F0
+    and $01
+    ora $03
+    sta $01
+    ; check second digit
+    lda $01
+    and #$F0
+    lsr
+    lsr
+    lsr
+    lsr
+    jsr check
+    asl
+    asl
+    asl
+    asl
+    sta $03
+    lda #$F
+    and $01
+    ora $03
+    sta $01
+    ; check third digit
+    lda $02
+    and #$F
+    jsr check
+    sta $03
+    lda #$F0
+    and $02
+    ora $03
+    sta $02
+    ; Shift
+    clc
+    rol $00
+    rol $01
+    rol $02
+    lda $00
+    cmp #0
+    bne dabble
+    rts
+
+nmi:
+    rti
\ No newline at end of file