From 9711b4ecc12cfa0a12c42c1446940b0282255923 Mon Sep 17 00:00:00 2001
From: Christophe Parent <christopheparent@thatspaceandtime.org>
Date: Thu, 28 Dec 2023 00:36:20 -0800
Subject: [PATCH] Remove CurrentBank as game runs in NMI handler only

---
 src/main.asm | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/src/main.asm b/src/main.asm
index 68a01fb..af69758 100644
--- a/src/main.asm
+++ b/src/main.asm
@@ -532,7 +532,6 @@ AltRegContentFlag     = $07ca
 
 ; mapper specific defines
 
-CurrentBank           = $15   ; The mapper is read-only; need to track its state separately
 CharsCopy             = $41   ; Reserving $41 and $42
 XStore                = $43   ; To store the X register
 
@@ -868,7 +867,7 @@ SkipMainOper:
     pla
     ora #%10000000            ; reactivate NMIs
     sta PPU_CTRL_REG1
-    rts                       ; we are done until the next frame!
+    rti                       ; we are done until the next frame!
 
 ;-------------------------------------------------------------------------------------
 
@@ -17309,24 +17308,21 @@ StartBankSwitch:
     jsr BankSwitch
     jmp Start
 
-; We make sure to have Bank 0 loaded at NMI, as the NMI code is located there; we switch back to the saved bank when we are done
+; We make sure to have Bank 0 loaded at NMI, as the NMI code is located there
 NonMaskableInterruptBankSwitch:
     ldx #$00
-    jsr BankSwitchNoSave
-    jsr NonMaskableInterrupt
-    ldx CurrentBank
-    jsr BankSwitchNoSave
-    rti
+    jsr BankSwitch
+    jmp NonMaskableInterrupt
 
 ; Area data is located in Bank 1; we switch back to Bank 0 when we are done
 AreaDataBankSwitch:
     stx XStore           ; We need to save the value of X because X is used for bank switching
     ldx #$01
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     lda (AreaData),y
     pha                  ; We need to save the byte because A is used for bank switching
     ldx #$00
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     pla
     ldx XStore
     rts
@@ -17335,11 +17331,11 @@ AreaDataBankSwitch:
 EnemyDataBankSwitch:
     stx XStore           ; We need to save the value of X because X is used for bank switching
     ldx #$01
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     lda (EnemyData),y
     pha                  ; We need to save the byte because A is used for bank switching
     ldx #$00
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     pla
     ldx XStore
     rts
@@ -17356,16 +17352,13 @@ CopyCharsBankSwitch:
 ; The sound engine is located in Bank 2; we switch back to Bank 0 when we are done
 SoundEngineBankSwitch:
     ldx #$02
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     jsr SoundEngine
     ldx #$00
-    jsr BankSwitchNoSave
+    jsr BankSwitch
     rts
 
 BankSwitch:
-    stx CurrentBank ; save the current bank in RAM so the NMI handler can restore it
-
-BankSwitchNoSave:
     lda BankTable,x ; remap from the convenient banks numbered 0 through 2 to the value needed by the hardware
     sta BankTable,x ; and write it to the corresponding entry, switching banks
     rts