Commodore 64 Kick Assembler消隐边框问题排查与解决

问题背景 #

我将一段ACME汇编脚本转换为Kick Assembler语法后，运行出现显示异常，有两个核心疑问：

• 如何修复显示异常问题？
• 自定义代码入口应插入何处，才能有效利用消隐后的屏幕区域？

调试过程与问题现象 #

1. 移除Wait宏后，边框能成功消隐，但屏幕顶部出现光栅线。
2. 调整代码并加入摇杆控制精灵的测试逻辑后，精灵可跨越上下边框，但画面出现黑色竖线伪影。

最终解决方案 #

通过添加以下两行代码，彻底解决了所有显示问题：

lda #$00
sta $3fff

初始转换代码 #

.macro Wait (v) {
    ldy #v
    dey
    bne *-1
}
 
* = $0801
.byte $0c, $08, $00, $00, $9e, $32, $30, $36, $31, $00, $00, $00

* = $080d
lda #$01
sta $3fff
sei
start:
    lda #$30
    cmp $d012
    bne *-3
    lda #$00
    sta $d011 
    Wait(24)
    lda #$0b
    sta $d011
    lda #$31
    cmp $d012
    bne *-3
    lda #$1b
    sta $d011 
    Wait(8)
    bit $ea
    ldx #$00
loop1:
    txa
    sta $d020
    sta $d021 
    Wait(9)
    inx
    cpx #254
    bne loop1
    asl $3fff
    bne start
    inc $3fff
    jmp start

调整后测试代码 #

* = $0801
BasicUpstart($080d);

.label JOYSTICK_2 = $dc00

.label UP       = %00000001
.label DOWN     = %00000010
.label LEFT     = %00000100
.label RIGHT    = %00001000
.label FIRE     = %00010000

.label JOYSTICK_2_IDLE = %01111111

.label SCREEN_RAM = $0400
.label SCREEN_CLEAR = $e544
.label SCREEN_BORDER_COLOR = $d020


.macro WAIT(duration) {
    ldy #duration
    dey
    bne *-1
}

* = $080d

lda #150
sta $d000 // Sprite 0的X坐标
lda #230
sta $d001 // Sprite 0的Y坐标

lda #LIGHT_RED
sta $d027 // Sprite 0颜色
lda #BLACK
sta $d025 // 精灵额外颜色1
lda #WHITE
sta $d026 // 精灵额外颜色2

lda #$80
sta $07f8 // Sprite 0指针索引
lda #%00000001 // 启用Sprite 0多色模式
sta $d01c
lda #%00000001 // 启用Sprite 0
sta $d015

lda #$01
sta $3fff
sei
start:
    lda #$fa
    cmp $d012
    bne *-3
    lda #$00
    sta $d011
    WAIT(22)
    lda #$1b
    sta $d011   
    jsr gameLoop

/*
loop1:
    txa
    sta $d020
    sta $d021
    WAIT(9)
    inx
    cpx #254
    bne loop1
    asl $3fff
    bne start
    inc $3fff
    jmp start*/

gameLoop:
    ldx #0
    slowDownLoop:
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        inx
        cpx #255
        bne slowDownLoop

    jsr readJoystick_2
    jsr start

readJoystick_2:
    lda JOYSTICK_2 // $dc00
    cmp #JOYSTICK_2_IDLE // %01111111
    beq joy2_IDLE
            jmp checkJoy2_UP
        joy2_IDLE:

        checkJoy2_UP:
            lda JOYSTICK_2
            and #UP
            beq joy2_UP
                jmp checkJoy2_DOWN
            joy2_UP:
                dec $d001

        checkJoy2_DOWN:
            lda JOYSTICK_2
            and #DOWN
            beq joy2_DOWN
                jmp checkJoy2_LEFT
            joy2_DOWN:
                inc $d001
            
        checkJoy2_LEFT:
            lda JOYSTICK_2
            and #LEFT
            beq joy2_LEFT
                jmp checkJoy2_RIGHT
            joy2_LEFT:
                dec $d000
            
        checkJoy2_RIGHT:
            lda JOYSTICK_2
            and #RIGHT
            beq joy2_RIGHT
                jmp checkJoy2_FIRE
            joy2_RIGHT:
                inc $d000
            
        checkJoy2_FIRE:
            lda JOYSTICK_2
            and #FIRE
            beq joy2_FIRE
                jmp doneReadJoystick_2
            joy2_FIRE:
                inc SCREEN_BORDER_COLOR
            
doneReadJoystick_2:
    rts

*=$2000
.import binary "testGuy.bin"

内容的提问来源于stack exchange，提问作者Black.Jack