Applecorn/mainmem.ldr.s

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4.6 KiB
ArmAsm
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* MAINMEM.LDR.S
* (c) Bobbi 2021 GPLv3
*
* Applecorn loader code. Runs in main memory.
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* Loads Acorn ROM file (16KB) from disk and writes it
* to aux memory starting at $08000. Copies Applecorn MOS
* to aux memory starting at AUXMOS1 and jumps to it.
* (Note that the MOS code will copy itself to $D000.)
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START JSR CROUT
JSR SETPRFX
JSR DISCONN
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LDA #$20 ; PAGE2 shadow on ROM3 GS
TRB $C035
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JSR ROMMENU
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LDA #>AUXADDR ; Address in aux
LDX #<AUXADDR
SEC ; Load into aux
JSR LOADCODE ; Load lang ROM
LDA #<:FDFILE
STA OPENPL+1
LDA #>:FDFILE
STA OPENPL+2
LDA #>FDRAWADDR ; Address in main
LDX #<FDRAWADDR
CLC ; Load into main
JSR LOADCODE
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LDA #<MOSSHIM ; Start address of MOS shim
STA A1L
LDA #>MOSSHIM
STA A1H
LDA #<MOSSHIM+$2000 ; End address of MOS shim
STA A2L
LDA #>MOSSHIM+$2000
STA A2H
LDA #<AUXMOS1 ; To AUXMOS1 in aux memory
STA A4L
LDA #>AUXMOS1
STA A4H
SEC ; Copy MOS from Main->Aux
JSR AUXMOVE
LDA #<RESET ; Set reset vector->RESET
STA RSTV
LDA #>RESET
STA RSTV+1
EOR #$A5 ; Checksum
STA RSTV+2
LDA #<GSBRK ; Set BRK vector in main mem
STA $3F0
LDA #>GSBRK
STA $3F0+1
JSR GFXINIT ; Initialize FDraw graphics
TSX ; Save SP at $0100 in aux
STA $C005 ; Write to aux
STX $0100
STA $C004 ; Write to main
>>> XF2AUX,AUXMOS1
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:FDFILE STR 'FDRAW.FAST' ; Filename for FDraw lib
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* Load image from file into memory
* On entry: OPENPL set up to point to file to load
* Load address in A,X
* Carry set->load to aux, carry clear->load to main
LOADCODE PHP ; Save carry flag
STA :ADDRH ; MSB of load address
STX :ADDRL ; LSB of load address
STZ :BLOCKS
JSR OPENFILE ; Open ROM file
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BCC :S1
LDX #$00
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:L1A LDA :CANTOPEN,X ; Part one of error msg
BEQ :S0
JSR COUT1
INX
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BRA :L1A
:S0 LDA OPENPL+1 ; Print filename
STA A1L
LDA OPENPL+2
STA A1H
LDY #$00
LDA (A1L),Y
STA :LEN
:L1B CPY :LEN
BEQ :ERR1
INY
LDA (A1L),Y
JSR COUT1
BRA :L1B
:ERR1 JSR CROUT
JSR BELL
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:SPIN BRA :SPIN
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:S1 LDA OPENPL+5 ; File reference number
STA READPL+1
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:L2 LDA #'.'+$80 ; Read file block by block
JSR COUT1
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JSR RDFILE
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BCS :CLOSE ; EOF (0 bytes left) or some error
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LDA #<BLKBUF ; Source start addr -> A1L,A1H
STA A1L
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LDA #>BLKBUF
STA A1H
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LDA #<BLKBUFEND ; Source end addr -> A2L,A2H
STA A2L
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LDA #>BLKBUFEND
STA A2H
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LDA :ADDRL ; Dest in aux -> A4L, A4H
STA A4L
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LDA :ADDRH
LDX :BLOCKS
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:L3 CPX #$00
BEQ :S2
INC
INC
DEX
BRA :L3
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:S2 STA A4H
PLP ; Recover carry flag
PHP
BCS :TOAUX
JSR MEMCPY ; Destination in main mem
BRA :S3
:TOAUX JSR AUXMOVE ; Carry already set (so to aux)
:S3 INC :BLOCKS
BRA :L2
:CLOSE LDA OPENPL+5 ; File reference number
STA CLSPL+1
JSR CLSFILE
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JSR CROUT
PLP
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RTS
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:ADDRL DB $00 ; Destination address (LSB)
:ADDRH DB $00 ; Destination address (MSB)
:BLOCKS DB $00 ; Counter for blocks read
:LEN DB $00 ; Length of filename
:CANTOPEN ASC "Unable to open "
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DB $00
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