From 5b03421e205b49f7ee35a9e6cbf1c64f1128acaa Mon Sep 17 00:00:00 2001
From: qwertymodo <qwertymodo@qwertymodo.com>
Date: Tue, 6 Feb 2018 22:38:27 -0800
Subject: [PATCH] MSU-1: Don't stall NMI while audio is busy loading, and wait
 for ending music to finish.

---
 hooks.asm |  3 +++
 msu.asm   | 77 ++++++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 57 insertions(+), 23 deletions(-)

diff --git a/hooks.asm b/hooks.asm
index 3bb2506..c780d70 100644
--- a/hooks.asm
+++ b/hooks.asm
@@ -1066,6 +1066,9 @@ spc_nmi:
     JML msu_main
     NOP
 spc_continue:
+
+org $0EE6EC ; <- E220 A922 - Bank0E.asm:2892 (SEP #$20)
+JSL.l ending_wait
 ;--------------------------------------------------------------------------------
 
 ;================================================================================
diff --git a/msu.asm b/msu.asm
index c2ff499..d49dada 100644
--- a/msu.asm
+++ b/msu.asm
@@ -58,6 +58,7 @@
 !REG_MUSIC_CONTROL = $012C
 !REG_CURRENT_TRACK = $0130
 !REG_CURRENT_COMMAND = $0133
+!REG_MSU_LOAD_FLAG = $7F509B
 
 !REG_SPC_CONTROL = $2140
 !REG_NMI_FLAGS = $4210
@@ -93,6 +94,35 @@ msu_main:
     SEP #$30
     LDX !REG_MUSIC_CONTROL
     BNE command_ff
+    LDA !REG_MSU_LOAD_FLAG
+    BEQ do_fade
+
+msu_check_busy:
+    LDA !REG_MSU_STATUS
+    BIT !FLAG_MSU_STATUS_AUDIO_BUSY
+    BEQ .ready
+    JML spc_continue
+.ready
+    LDA !REG_MSU_STATUS
+    BIT !FLAG_MSU_STATUS_TRACK_MISSING
+    BNE spc_fallback
+    LDA !VAL_VOLUME_FULL
+    STA !REG_TARGET_VOLUME
+    STA !REG_CURRENT_VOLUME
+    STA !REG_MSU_VOLUME
+    LDA !REG_MSU_LOAD_FLAG
+    STA !REG_MSU_CONTROL
+    LDA #$00
+    STA !REG_MSU_LOAD_FLAG
+    JML spc_continue
+
+spc_fallback:
+    STZ !REG_MSU_CONTROL
+    STZ !REG_CURRENT_MSU_TRACK
+    STZ !REG_TARGET_VOLUME
+    STZ !REG_CURRENT_VOLUME
+    STZ !REG_MSU_VOLUME
+    JML spc_continue
     
 do_fade:
     LDA !REG_CURRENT_VOLUME
@@ -156,28 +186,29 @@ load_track:
     STX !REG_MSU_TRACK_LO
     STZ !REG_MSU_TRACK_HI
     STZ !REG_MSU_CONTROL
-    LDA !VAL_VOLUME_FULL
-    STA !REG_TARGET_VOLUME
-    STA !REG_CURRENT_VOLUME
-    STA !REG_MSU_VOLUME
-
-msu_check_busy:
-    LDA !REG_MSU_STATUS
-    BIT !FLAG_MSU_STATUS_AUDIO_BUSY
-    BNE msu_check_busy
-    BIT !FLAG_MSU_STATUS_TRACK_MISSING
-    BEQ msu_play
-
-spc_fallback:
-    STZ !REG_MSU_CONTROL
-    STZ !REG_CURRENT_MSU_TRACK
-    STZ !REG_TARGET_VOLUME
-    STZ !REG_CURRENT_VOLUME
-    STZ !REG_MSU_VOLUME
+    LDA.l track_list,x
+    STA !REG_MSU_LOAD_FLAG
+    STX !REG_CURRENT_MSU_TRACK
     JML spc_continue
 
-msu_play:
-    LDA.l MSUTrackList, X
-    STA !REG_MSU_CONTROL
-    STX !REG_CURRENT_MSU_TRACK
-    JML spc_continue
\ No newline at end of file
+
+ending_wait:
+    rep #$20
+    lda !REG_MSU_ID_01
+    cmp !VAL_MSU_ID_01
+    bne .done
+    lda !REG_MSU_ID_23
+    cmp !VAL_MSU_ID_23
+    bne .done
+    lda !REG_MSU_ID_45
+    cmp !VAL_MSU_ID_45
+    bne .done
+    sep #$20
+.wait
+    lda !REG_MSU_STATUS
+    bit !FLAG_MSU_STATUS_AUDIO_PLAYING
+    bne .wait
+.done
+    sep #$20
+    lda #$22
+    rtl