mirror of
https://github.com/ksherlock/itty-bitty-vtty.git
synced 2024-11-21 20:30:56 +00:00
118 lines
1.2 KiB
ArmAsm
118 lines
1.2 KiB
ArmAsm
*
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* boot block.
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*
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* loaded at $0800
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* relocates everything to $6000, loads extra blocks, and runs main.
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xc
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xc
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rel
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* org $0800
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ORG equ $6000
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*MAX_BLOCK equ 6
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SLOT equ $00
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CMD equ $42
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UNIT equ $43
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BUFFER equ $44
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BLOCK equ $46
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ext main
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ext MAXBLOCKS
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boot
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mx %11
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db $01 ; prodos boot id
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* slot 5 = x = $50, a = $3178
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* slot 6 = x = $60, a = $8401
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* stx :unit
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* txa
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* lsr
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* lsr
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* lsr
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* lsr
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* ora #$c0
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ldy #END-boot
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:cp lda $0800,y ; boot,y
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sta ORG,y
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dey
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bne :cp
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jmp ORG+:entry-boot
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:entry stx UNIT
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txa
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lsr
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lsr
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lsr
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lsr
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ora #$c0
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sta :prodos+2
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stz SLOT
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sta SLOT+1
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ldy #1
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lda (SLOT),y
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cmp #$20
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bne noboot
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ldy #3
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lda (SLOT),y
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bne noboot
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ldy #5
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lda (SLOT),y
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cmp #$03
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bne noboot
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ldy #$ff
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lda (SLOT),y
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sta :prodos+1
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lda #1 ; read block
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sta CMD
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sta BLOCK
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stz BLOCK+1
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stz BUFFER
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lda #>{ORG+512} ; $0800+512
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sta BUFFER+1
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:read
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jsr :prodos ; block 1
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bcs noboot
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inc BLOCK
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inc BUFFER+1
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inc BUFFER+1
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lda BLOCK
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cmp #MAXBLOCKS
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bcc :read
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bra :ok
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:prodos jmp $0000
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:ok
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jmp main
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noboot
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ldx #0
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:cout lda :str,x
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beq :wai
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jsr $fded
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inx
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bra :cout
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:wai wai
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bra :wai
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:str asc "** BOOT ERROR **",00
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END
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err *-boot>$ff
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* fill to end of block since only 255 bytes relocated.
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ds boot+512-*
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sav boot.L |