214 lines
5.5 KiB
ArmAsm
214 lines
5.5 KiB
ArmAsm
* APPLECORN.S
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* (c) Bobbi 2021 GPLv3
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*
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* Load an Acorn BBC Micro ROM in aux memory and
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* Provide an environment where it can run
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*
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* Assembled with the Merlin 8 v2.58 assembler on Apple II.
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XC ; 65c02
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ORG $4000 ; Load addr of loader in main memory
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; Clear of first HGR frame buffer
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* Monitor routines
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BELL EQU $FBDD
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PRBYTE EQU $FDDA
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COUT1 EQU $FDED
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CROUT EQU $FD8E
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HOME EQU $FC58
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AUXMOVE EQU $C311
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XFER EQU $C314
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* Monitor ZP locations
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A1L EQU $3C
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A1H EQU $3D
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A2L EQU $3E
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A2H EQU $3F
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A4L EQU $42
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A4H EQU $43
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* Used by XFER
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STRTL EQU $3ED
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STRTH EQU $3EE
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* Reset vector (2 bytes + 1 byte checksum)
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RSTV EQU $3F2
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* IRQ vector
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A2IRQV EQU $3FE
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* MLI entry point
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MLI EQU $BF00
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* IO Buffer for reading file (1024 bytes)
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IOBUF0 EQU $0C00 ; For loading/saving, OSFILE, *.
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IOBUF1 EQU $1000 ; Four open files for langs
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IOBUF2 EQU $1400
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IOBUF3 EQU $1800
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IOBUF4 EQU $1C00
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* 512 byte buffer sufficient for one disk block
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BLKBUF EQU $9000 ; Can't use $400 as ProDOS uses
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BLKBUFEND EQU $9200 ; 'hidden' bytes within screen
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* 512 byte buffer for file copy (*COPY)
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COPYBUF EQU $9200 ; File copy needs separate buffer
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*COPYBUFEND EQU $9400
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* Location of FDraw library in main memory
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FDRAWADDR EQU $9400
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* Address in aux memory where ROM will be loaded
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AUXADDR EQU $8000
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* Address in aux memory where the MOS shim is located
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AUXMOS1 EQU $2000 ; Temp staging area in Aux
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EAUXMOS1 EQU $5000 ; End of staging area
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AUXMOS EQU $D000 ; Final location in aux LC
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* Called by code running in main mem to invoke a
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* routine in aux memory
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XF2AUX MAC
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LDX $C08B ; R/W LC RAM, bank 1
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LDX $C08B
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LDX #<]1
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STX STRTL
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LDX #>]1
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STX STRTH
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SEI ; Disable IRQ before XFER
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SEC ; Use aux memory
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BIT $FF58 ; Set V: use alt ZP and LC
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JMP XFER
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EOM
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* Called by code running in aux mem to invoke a
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* routine in main memory
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XF2MAIN MAC
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LDX STRTL
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STX STRTBCKL
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LDX STRTH
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STX STRTBCKH
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LDX #<]1
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STX STRTL
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LDX #>]1
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STX STRTH
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SEI ; Disable IRQ before XFER
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TSX
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STX $0101 ; Save alt SP
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LDX $0100 ; Load main SP into X
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CLC ; Use main mem
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CLV ; Use main ZP and LC
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JMP XFER
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EOM
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* Macro called on re-entry to aux memory
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* Careful: This enables IRQ - not for use in ISR
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ENTAUX MAC
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LDX $0101 ; Recover alt SP
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TXS
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CLI ; Re-enable IRQ after XFER
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LDX STRTBCKL
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STX STRTL
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LDX STRTBCKH
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STX STRTH
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EOM
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* Macro called on re-entry to main memory
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* Careful: This enables IRQ - not for use in ISR
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ENTMAIN MAC
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TXS ; Main SP already in X
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LDX $C081 ; Bank in ROM
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LDX $C081
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CLI ; Re-enable IRQ after XFER
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EOM
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* Macro called on re-entry to aux memory
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* For use in interrupt handlers (no CLI!)
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IENTAUX MAC
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LDX $0101 ; Recover alt SP
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TXS
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LDX STRTBCKL
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STX STRTL
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LDX STRTBCKH
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STX STRTH
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EOM
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* Macro called on re-entry to main memory
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* For use in interrupt handlers (no CLI!)
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IENTMAIN MAC
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TXS ; Main SP already in X
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LDX $C081 ; Bank in ROM
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LDX $C081
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EOM
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* Enable writing to main memory (for code running in aux)
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WRTMAIN MAC
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SEI ; Keeps IRQ handler easy
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STA $C004 ; Write to main memory
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EOM
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* Go back to writing to aux (for code running in aux)
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WRTAUX MAC
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STA $C005 ; Write to aux memory
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CLI ; Normal service resumed
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EOM
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* Manually enable AltZP (for code running in main)
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ALTZP MAC
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SEI ; Disable IRQ when AltZP on
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LDA $C08B ; R/W LC bank 1
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LDA $C08B
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STA $C009 ; Alt ZP and LC
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EOM
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* Manually disable AltZP (for code running in main)
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MAINZP MAC
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STA $C008 ; Main ZP and LC
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LDA $C081 ; Bank ROM back in
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LDA $C081
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CLI ; Turn IRQ back on
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EOM
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* Code is all included from PUT files below ...
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* ... order matters!
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PUT MAINMEM.LDR
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PUT MAINMEM.MENU
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PUT MAINMEM.FSEQU
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PUT MAINMEM.INIT
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PUT MAINMEM.SVC
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PUT MAINMEM.PATH
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PUT MAINMEM.WILD
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PUT MAINMEM.LISTS
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PUT MAINMEM.MISC
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PUT AUXMEM.MOSEQU
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PUT AUXMEM.INIT
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PUT AUXMEM.VDU
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PUT AUXMEM.GFX
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PUT AUXMEM.HOSTFS
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PUT AUXMEM.OSCLI
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PUT AUXMEM.BYTWRD
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PUT AUXMEM.CHARIO
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PUT AUXMEM.MISC
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* Automatically save the object file:
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SAV APPLECORN
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