57 lines
772 B
ArmAsm
57 lines
772 B
ArmAsm
!source "constants.s"
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!source "basic-boot.s"
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+start_at $0900
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sei ; no interrupts pls
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ldx #$00 ; Screen colours
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stx bdcol
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ldx #$08
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stx bgcol
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jsr $e544 ; clear screen
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;lda < message ; print message
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;pha
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;lda > message
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;pha
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jsr print_string
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;pla
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;pla
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ldx #$01 ; start triangle wave
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ldy #$11
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stx ch1_freq_hi
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sty ch1_freq_lo
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ldx #$11
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stx ch1_ctl
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.loop
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inc bdcol
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lda inputb ; Scans the keyboard buffer
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cmp #$EF ; If user presses Space ($ef) then quit
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bne .loop
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ldx #$08 ; kill sound
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stx ch1_ctl
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rts
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print_string:
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;lda message
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;sta PSL + 2
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;lda > message
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;sta PSL + 1
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ldx #$00
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PSL lda message, x
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cmp #$0 ; return on null terminator
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beq +
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sta screen + rowlen, x
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inx
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jmp PSL
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+ rts
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message !scr "welcome to scat os", 0
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