progress on the safe copy routine
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261
tarot.asm
261
tarot.asm
@ -9,11 +9,32 @@ DEF SCENE_SETUP EQU $FF81
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DEF SCENE_UPDATE EQU SCENE_SETUP + 4 ; call then ret is 3+1 bytes
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DEF SCENE_DRAW EQU SCENE_UPDATE + 4
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DEF SCENE_TEARDOWN EQU SCENE_DRAW + 4
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DEF rMYBTN EQU $FF90
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DEF rMYBTN EQU $FFA0
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DEF rMYBTNP EQU rMYBTN + 1
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DEF vSelectedTileIndex EQU $FF90+2
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DEF vPreviousCardIndex EQU $FF90+3
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DEF INTERRUPT_LCD EQU $FF91
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; tile index variables
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DEF vSelectedTileIndex EQU $FFA0+2
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DEF vPreviousCardIndex EQU $FFA0+3
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; variables for safe transfer async function
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DEF vSafeCopySource EQU $FFA0+4
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DEF vSafeCopyDest EQU vSafeCopySource + 2
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DEF vSafeCopyCount EQU vSafeCopyDest + 2 ; check this for safe transfer being complete
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; stash previous interrupt state before using the interrupts
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DEF vSafeCopyLYC EQU vSafeCopyCount + 2 ; stashes $FF45, the LYC register
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DEF vSafeCopySTAT EQU vSafeCopyLYC + 1 ; stashes $FF41, the STAT register
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DEF vSafeCopyInterruptFirst EQU vSafeCopySTAT + 1 ; stashes $0048 the STAT interrupt
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DEF vSafeCopyInterruptSecond EQU vSafeCopyInterruptFirst + 1
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DEF vSafeCopyInterruptEnable EQU vSafeCopyInterruptSecond + 1 ; stashes $FFFF, which interrupts are enabled
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INCLUDE "hardware.inc"
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SECTION "Interrupts", ROM0[$0]
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ds $48 - @, 0
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call INTERRUPT_LCD - 1
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ret
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SECTION "Header", ROM0[$100]
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@ -35,6 +56,8 @@ EntryPoint:
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ld [hl], a
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ld hl, SCENE_TEARDOWN - 1
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ld [hl], a
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ld hl, INTERRUPT_LCD - 1
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ld [hl], a
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ld a, [Instructions + 3] ; get the value of a ret instruction
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ld hl, SCENE_SETUP + 2
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@ -45,6 +68,8 @@ EntryPoint:
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ld [hl], a
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ld hl, SCENE_TEARDOWN + 2
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ld [hl], a
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ld hl, INTERRUPT_LCD + 2
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ld [hl], a
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; set up our scene vectors
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ld hl, SCENE_SETUP
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@ -72,6 +97,14 @@ EntryPoint:
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ld a, d
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ld [hl+], a
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; set up the interrupt vector to just be ret.
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ld hl, INTERRUPT_LCD
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ld de, INTERRUPT_LCD + 2
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ld a, e
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ld [hl+], a
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ld a, d
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ld [hl+], a
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; Do not turn the LCD off outside of VBlank
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WaitVBlank:
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ld a, [rLY]
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@ -81,6 +114,7 @@ WaitVBlank:
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call SCENE_SETUP - 1
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Loop:
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di
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ld hl, rP1
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ld [hl], P1F_GET_DPAD
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ld a, [hl]
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@ -107,13 +141,15 @@ Loop:
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ld a, b
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ld [rMYBTN], a
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di
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call SCENE_UPDATE - 1
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ei
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ld b, 144
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call AwaitLine
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di
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call SCENE_DRAW - 1
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ei
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jp Loop
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@ -126,17 +162,17 @@ CardReadSetup:
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ld hl, UITiles ; source
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ld de, $8800 ; destination of copy
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ld bc, UITilesEnd - UITiles ; length to copy
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call CopyRange
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call CopyRangeUnsafe
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ld hl, LetterTiles ; map the small font into vram at ascii locations
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ld de, $8000 + (127 + $21)*16
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ld bc, LetterTilesEnd - LetterTiles
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call CopyRange
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call CopyRangeUnsafe
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ld hl, BigLetterTiles
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ld de, $8000 + (128 + 16 + 32)*16
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ld bc, BigLetterTilesEnd - BigLetterTiles
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; call CopyRange
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; call CopyRangeUnsafe
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ld de, UITilemap ; origin
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ld hl, $9800 ; destination
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@ -150,11 +186,6 @@ CardReadSetup:
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ld c, 8
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call CopyTilesToMap
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ld a, $FF
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ld [vPreviousCardIndex], a
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ld a, 0
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call LoadCardData
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; Turn the LCD on
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ld a, LCDCF_BLK01 | LCDCF_ON | LCDCF_BGON
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ld [rLCDC], a
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@ -163,43 +194,44 @@ CardReadSetup:
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ld a, %11100100
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ld [rBGP], a
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ld a, $FF
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ldh [vPreviousCardIndex], a
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ld a, 0
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ldh [vSelectedTileIndex], a
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call LoadCardData
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ei
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ret ; return from cardreadsetup
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CardReadUpdate:
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ldh a, [rMYBTNP]
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and a, %0000_1000 ; check if down is held
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and a, %0000_1000 ; select the down key
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jp z, CardReadUpdateDoneDown
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ldh a, [vSelectedTileIndex]
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inc a ; increment when they press down because the stack has card 0 at the top
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ldh [vSelectedTileIndex], a
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CardReadUpdateDoneDown:
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ldh a, [rMYBTNP]
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and a, %0000_0100
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and a, %0000_0100 ; select the up key
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jp z, CardReadUpdateDoneUp
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ldh a, [vSelectedTileIndex]
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dec a ; decrement when they press up because the stack has card 0 at the top
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ldh [vSelectedTileIndex], a
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CardReadUpdateDoneUp:
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ldh a, [vSelectedTileIndex]
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cp a, 22
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cp a, 2
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jp nz, CardReadUpdateDoneZero
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ld a, 0
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ldh [vSelectedTileIndex], a
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CardReadUpdateDoneZero:
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cp a, $FF
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jp nz, CardReadUpdateReturn
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ld a, 21
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ld a, 1
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ldh [vSelectedTileIndex], a
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CardReadUpdateReturn:
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ret
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CardReadDraw:
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ldh a, [vSelectedTileIndex]
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call LoadCardData
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ld b, 11 ; 11 rows, and we stop before drawing row zero
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ld b, 1 ; 11 rows, and we stop before drawing row zero
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ld hl, $9800+32*4+19 ; start point
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ld de, 32 ; stride
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CardReadDrawCopyTile:
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@ -240,33 +272,23 @@ CardReadDraw_PickTileWithTop:
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ld a, $82
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ld [hl], a
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CardReadDrawReturn:
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ld a, [vSelectedTileIndex]
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call LoadCardData
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ldh a, [vSelectedTileIndex]
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ld hl, vPreviousCardIndex
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cp a, [hl]
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call nz, LoadCardData ; only load new card data if the selected card has changed
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ret
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CardReadTeardown:
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ret
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LoadCardData:
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ld hl, vPreviousCardIndex
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cp a, [hl]
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ret z
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ld a, [vSelectedTileIndex]
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ld [vPreviousCardIndex], a
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ld [vSelectedTileIndex], a
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ld a, [rLCDC]
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cp 0
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jp z, LoadCardData_DoneTurningOff
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ld b, 144
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call AwaitLine ; put the line you want to reach in b
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ld a, 0
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ld [rLCDC], a ; turn off the lcd so we don't cause memory corruption
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call AwaitLine ; wait for vblank before starting to work
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LoadCardData_DoneTurningOff:
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ld a, [vSelectedTileIndex]
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ld b, 0
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ld c, a ; load bc from a. coming into this we have the number of the card in the card array in a
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ld hl, Cards + 1 ; skip the length prefix
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@ -316,7 +338,7 @@ LoadCardData_DoneTurningOff:
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ld de, $8000 ; always load tile data into the same spot in vram
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call CopyRange
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call CopyRangeSafe
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pop hl
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ld a, [hl+]
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@ -337,8 +359,7 @@ LoadCardData_DoneTurningOff:
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ld c, 8 ; width
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call CopyTilesToMap
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ld a, LCDCF_BLK01 | LCDCF_ON | LCDCF_BGON
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ld [rLCDC], a
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ret
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Instructions:
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@ -368,7 +389,7 @@ AwaitLine: ; put the line you want to reach in b
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jp nz, AwaitLine
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ret
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CopyRange:
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CopyRangeUnsafe:
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; hl is source
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; de is destination
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; bc is length to copy
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@ -378,7 +399,161 @@ CopyRange:
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dec bc
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ld a, b
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or a, c ; check if bc is zero
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jp nz, CopyRange
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jp nz, CopyRangeUnsafe
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ret
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CopyRangeSafe:
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; hl is source
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; de is destination
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; bc is length to copy
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; copy an array of bytes to a destination in memory.
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; this is completely different from CopyRangeUnsafe.
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; this initiates an asynchronous, interrupt-driven copy of BC bytes of memory
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; from HL to DE.
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; it may return a memory address to look at for progress of the transfer,
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; or else it's just going to do it with a hard-coded address.
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; check the transfer status address for zero; when it's zero, the transfer is done!
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; this works by using the STAT interrupt in LYC mode to interrupt its own execution at
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; two scanlines inside the vblank interval to know when to start and stop.
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; stash arguments in memory
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di
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ld a, l
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ldh [vSafeCopySource], a
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ld a, h
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ldh [vSafeCopySource+1], a
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ld a, e
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ldh [vSafeCopyDest], a
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ld a, d
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ldh [vSafeCopyDest+1], a
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ld a, c
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ldh [vSafeCopyCount], a
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ld a, b
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ldh [vSafeCopyCount+1], a
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; stash interrupt state in memory
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ldh a, [$ff41]
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ldh [vSafeCopySTAT], a ; stashes $FF41, the STAT register
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ldh a, [$ff45]
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ldh [vSafeCopyLYC], a ; stashes $FF45, the LYC register
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ld a, [INTERRUPT_LCD]
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ld [vSafeCopyInterruptFirst], a
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ld a, [INTERRUPT_LCD + 1]
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ld [vSafeCopyInterruptSecond], a ; stashes $0048 the STAT interrupt handler
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ld a, [$ffff]
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and a, %0000_0010
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ld [vSafeCopyInterruptEnable], a ; stashes whether LCD interrupt are enabled
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ld a, 148 ; adjust this to change timing of copy
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ld [$ff45], a
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ld hl, CopyRangeSafe_EnterSafeMode
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ld a, l
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ld [INTERRUPT_LCD], a
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ld a, h
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ld [INTERRUPT_LCD + 1], a; set interrupt handler to "ENTER SAFE MODE"
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ld a, 148 ; CHANGE ME TO ADJUST SAFE TRANSFER TIMING
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ld [$ff45], a
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ld hl, $ffff
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set 1, [hl]
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ld a, %0100_0000
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ld [$ff41], a
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ld hl, vSafeCopyCount
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ei
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ret ; return address of bytes remaining to copy
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CopyRangeSafe_EnterSafeMode:
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ld hl, CopyRangeSafe_ExitSafeMode
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ld a, l
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ld [INTERRUPT_LCD], a
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ld a, h
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ld [INTERRUPT_LCD+1], a
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ld a, 153 ; CHANGE ME TO ADJUST SAFE TRANSFER TIMING
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ld [$ff45], a ; set lcd interrupt handler to EXIT SAFE MODE on line 153
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ldh a, [vSafeCopySource]
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ld l, a
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ldh a, [vSafeCopySource+1]
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ld h, a ; fetch the source
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ldh a, [vSafeCopyDest]
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ld e, a
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ldh a, [vSafeCopyDest+1]
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ld d, a ; fetch the dest
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ldh a, [vSafeCopyCount]
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ld c, a
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ldh a, [vSafeCopyCount+1]
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ld b, a ; fetch the count
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; before starting transfer, make sure the zero flag is false.
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ld a, 1
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cp a, 0
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CopyRangeSafe_TransferLoop:
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ei
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nop ; ei only sets the flag one instruction later apparently. safety nop!
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nop
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di ; process interrupts
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jp z, CopyRangeSafe_CleanUp ; zero flag will only be set if the exitsafemode handler fired
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ld a, [hl+]
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ld [de], a ;
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inc de
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dec bc
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ld a, b
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or a, c
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jp nz, CopyRangeSafe_TransferLoop
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jp CopyRangeSafe_Done
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CopyRangeSafe_ExitSafeMode:
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ld a, 0
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cp a, 0 ; set the zero flag, which we're using as a signal to stop transferring
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reti ; set a to zero and set the zero flag true. now the transfer loop will end
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CopyRangeSafe_CleanUp:
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ld a, l
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ldh [vSafeCopySource], a
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ld a, h
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ldh [vSafeCopySource+1], a ; store new source
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ld a, e
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ldh [vSafeCopyDest], a
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ld a, d
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ldh [vSafeCopyDest+1], a ; store new dest
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ld a, c
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ldh [vSafeCopyCount], a
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ld a, b
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ldh [vSafeCopyCount+1], a ; store new count
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ld hl, CopyRangeSafe_EnterSafeMode
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ld a, l
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ld [INTERRUPT_LCD], a
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ld a, h
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ld [INTERRUPT_LCD+1], a
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ld a, 148 ; CHANGE ME TO ADJUST SAFE TRANSFER TIMING
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ld [$ff45], a ; set lcd interrupt handler to ENTER SAFE MODE on line 148
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reti ; we're done with this memcpy cycle so we return from interrupt.
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CopyRangeSafe_Done: ; called when the complete transfer is finished,
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; this restores interrupts to how they were.
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; stash interrupt state in memory
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ldh a, [vSafeCopySTAT]
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ldh [$ff41], a
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ldh a, [vSafeCopyLYC]
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ldh [$ff45], a
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ldh a, [vSafeCopyInterruptFirst]
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ld [INTERRUPT_LCD], a
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ldh a, [vSafeCopyInterruptSecond]
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ldh [INTERRUPT_LCD+1], a
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ld hl, $ffff
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ld a, [hl]
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cpl
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set 1, a
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cpl ; turn off the lcd interrupt enable
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ld [hl], a
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ld a, [vSafeCopyInterruptEnable]
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cp a, 0 ; if the stashed enable was 0 return. if the stashed enable was 1 then turn it on
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jp z, CopyRangeSafe_Return
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set 1, [hl] ; turn on the lcd interrupt
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CopyRangeSafe_Return:
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ret
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CopyTilesToMap:
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@ -438,7 +613,7 @@ TheFool:
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dw FoolTilesEnd - FoolTiles
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dw FoolTiles
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dw FoolMapEnd - FoolMap
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dw FoolMap, FoolMapEnd
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dw FoolMap
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FoolTiles:
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db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
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db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$01,$00,$01,$00,$02
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