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89 lines
1.4 KiB
ArmAsm
89 lines
1.4 KiB
ArmAsm
;
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; loader
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; A very simplistic code loader designed to manage
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; GS code under ProDOS 8 (if it's good enough for Will Harvey...)
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;
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; Created by Quinn Dunki on 7/29/17
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;
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.include "equates.s"
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.include "macros.s"
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LOADBUFFER = $1000 ; Clear of this loader code
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BUFFERSIZE = $8200 ; About max size we can fit between buffer and this loader code
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MAINENTRY = $020800
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.org $800
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main:
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OP8 ; We launch in emulation. Stay there for now
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; Open the main code file
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jsr PRODOS
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.byte $c8
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.addr fileOpenCode
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bne ioError
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; Load the code into bank 0
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jsr PRODOS
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.byte $ca
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.addr fileReadCode
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bne ioError
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; Close the file
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jsr PRODOS
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.byte $cc
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.addr fileCloseCode
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NATIVE
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; Copy code into bank 2
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mainCopyStart:
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ldx #0
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mainCopyLoop:
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lda LOADBUFFER,x
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mainCopyDest:
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sta MAINENTRY,x
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inx
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inx
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cpx #LOADBUFFER+BUFFERSIZE
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bne mainCopyLoop
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; Set up a long jump into bank 2, and
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; a way for game code to get back here to exit
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; properly to ProDOS 8
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lda #returnToProDOS
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sta PRODOSRETURN
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jml MAINENTRY
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returnToProDOS:
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SYNCDBR
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EMULATION
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rts
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ioError:
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brk
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fileOpenCode:
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.byte 3
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.addr codePath
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.addr $9200 ; 1k below BASIC.SYSTEM
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.byte 0 ; Result (file handle)
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.byte 0 ; Padding
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fileReadCode:
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.byte 4
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.byte 1 ; File handle (we know it's gonna be 1)
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.addr LOADBUFFER
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.word BUFFERSIZE
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.word 0 ; Result (bytes read)
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fileCloseCode:
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.byte 1
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.byte 1 ; File handle (we know it's gonna be 1)
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codePath:
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pstring "/GSAPP/CODEBANK"
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