mirror of
https://github.com/whscullin/apple2js.git
synced 2024-01-12 14:14:38 +00:00
84 lines
1.4 KiB
ArmAsm
84 lines
1.4 KiB
ArmAsm
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ORG $C700
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; Slot scan ZP addresses
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SCAN_LO EQU $00
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SCAN_HI EQU $01
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; ProDOS
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COMMAND EQU $42
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UNIT EQU $43
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ADDRESS_LO EQU $44
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ADDRESS_HI EQU $45
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BLOCK_LO EQU $46
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BLOCK_HI EQU $47
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MSLOT EQU $7F8
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; Slot I/O addresses
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STATUS EQU $C080
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; ROM addresses
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BASIC EQU $E000
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SLOOP EQU $FABA ; Resume boot scan
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ROMRTS EQU $FF58
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BOOT EQU $0801
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LDX #$20 ; $20 $00 $03 $00 - Smartport signature
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LDX #$00 ; $20 $00 $03 $3C - Vanilla disk signature
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LDX #$03
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LDX #$00 ; Override with $3C for DumbPort
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; Determine our slot
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JSR ROMRTS
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TSX
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LDA $0100,X
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STA MSLOT ; $Cn
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ASL
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ASL
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ASL
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ASL
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TAY ; $n0
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; Load the disk status bits
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LDA STATUS,Y
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LSR ; Check for Disk 1
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BCS DISKREADY ; Boot from Disk 1
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LDA SCAN_LO
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BNE GO_BASIC
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LDA SCAN_HI
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CMP MSLOT
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BNE GO_BASIC
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JMP SLOOP ; Go back to scanning
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GO_BASIC JMP BASIC ; Go to basic
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; Boot routine
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DISKREADY LDX #$01 ; Read
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STX COMMAND
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DEX
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STX BLOCK_LO ; Block 0
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STX BLOCK_HI
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STX ADDRESS_LO ; Into $800
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LDX #$08
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STX ADDRESS_HI
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LDA MSLOT
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PHA ; Save slot address
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PHA ; RTS address hi byte
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LDA #REENTRY - 1
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PHA ; RTS address lo byte
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CLV
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BVC BLOCK_ENT
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REENTRY PLA ; Restore slot address
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ASL ; Make I/O register index
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ASL
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ASL
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ASL
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TAX
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JMP BOOT
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DS 2
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BLOCK_ENT RTS
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DS 2
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SMARTPOINT_ENT RTS
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PADDING DS $C7FE - PADDING
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ORG $C7FE
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FLAGS DFB $D7
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ENTRY_LO DFB BLOCK_ENT
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END
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