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102 lines
2.1 KiB
ArmAsm
102 lines
2.1 KiB
ArmAsm
;
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; Startup code for cc65 (C16 version)
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;
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; Note: The C16 is actually the Plus/4 with just 16KB of memory. So, many
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; things are similar here; and, we even use the plus4.inc include file.
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;
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.export _exit
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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import initlib, donelib
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.import callmain, zerobss
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.import MEMTOP, RESTOR, BSOUT, CLRCH
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.importzp ST
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.include "zeropage.inc"
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.include "plus4.inc"
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; ------------------------------------------------------------------------
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; Startup code
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.segment "STARTUP"
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Start:
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; Save the zero-page locations that we need.
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ldx #zpspace-1
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L1: lda sp,x
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sta zpsave,x
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dex
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bpl L1
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; Switch to the second charset.
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lda #14
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jsr BSOUT
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; Clear the BSS data.
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jsr zerobss
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; Save some system stuff; and, set up the stack.
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tsx
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stx spsave ; save system stk ptr
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sec
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jsr MEMTOP ; Get top memory
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cpy #$80 ; We can only use the low 32K :-(
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bcc MemOk
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ldy #$80
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ldx #$00
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MemOk: stx sp
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sty sp+1 ; set argument stack ptr
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; Call the module constructors.
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jsr initlib
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; Push the command-line arguments; and, call main().
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jsr callmain
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; Call the module destructors. This is also the exit() entry.
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_exit: pha ; Save the return code on stack
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jsr donelib ; Run module destructors
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; Copy back the zero-page stuff.
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ldx #zpspace-1
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L2: lda zpsave,x
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sta sp,x
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dex
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bpl L2
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; Store the return code into BASIC's status variable.
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pla
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sta ST
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; Restore the stack pointer.
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ldx spsave
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txs
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; Back to BASIC.
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rts
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; ------------------------------------------------------------------------
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.segment "ZPSAVE"
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zpsave: .res zpspace
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; ------------------------------------------------------------------------
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.bss
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spsave: .res 1
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