mirror of
https://github.com/cc65/cc65.git
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151 lines
3.0 KiB
ArmAsm
151 lines
3.0 KiB
ArmAsm
;
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; Startup code for cc65 (Vic20 version)
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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, callirq
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.import zerobss, push0
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.import callmain
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.import RESTOR, BSOUT, CLRCH
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.import __INTERRUPTOR_COUNT__
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.import __RAM_START__, __RAM_SIZE__ ; Linker generated
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.include "zeropage.inc"
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.include "vic20.inc"
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; ------------------------------------------------------------------------
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; BASIC header with a SYS call
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.segment "EXEHDR"
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.word Head ; Load address
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Head: .word @Next
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.word .version ; Line number
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.byte $9E ; SYS token
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.byte <(((Start / 1000) .mod 10) + '0')
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.byte <(((Start / 100) .mod 10) + '0')
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.byte <(((Start / 10) .mod 10) + '0')
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.byte <(((Start / 1) .mod 10) + '0')
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.byte $00 ; End of BASIC line
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@Next: .word 0 ; BASIC end marker
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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 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 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 system stuff and setup the stack
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tsx
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stx spsave ; Save the system stack ptr
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lda #<(__RAM_START__ + __RAM_SIZE__)
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sta sp
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lda #>(__RAM_START__ + __RAM_SIZE__)
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sta sp+1 ; Set argument stack ptr
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; If we have IRQ functions, chain our stub into the IRQ vector
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lda #<__INTERRUPTOR_COUNT__
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beq NoIRQ1
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lda IRQVec
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ldx IRQVec+1
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sta IRQInd+1
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stx IRQInd+2
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lda #<IRQStub
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ldx #>IRQStub
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sei
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sta IRQVec
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stx IRQVec+1
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cli
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; Call module constructors
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NoIRQ1: jsr initlib
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; Push arguments and call main()
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jsr callmain
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; Back from main (This is also the _exit entry). Run module destructors
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_exit: jsr donelib
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; Reset the IRQ vector if we chained it.
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pha ; Save the return code on stack
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lda #<__INTERRUPTOR_COUNT__
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beq NoIRQ2
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lda IRQInd+1
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ldx IRQInd+2
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sei
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sta IRQVec
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stx IRQVec+1
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cli
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; Copy back the zero page stuff
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NoIRQ2: 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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; Place the program return code into ST
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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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; Reset changed vectors, back to basic
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jmp RESTOR
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; ------------------------------------------------------------------------
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; The IRQ vector jumps here, if condes routines are defined with type 2.
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IRQStub:
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cld ; Just to be sure
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jsr callirq ; Call the functions
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jmp IRQInd ; Jump to the saved IRQ vector
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; ------------------------------------------------------------------------
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; Data
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.data
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IRQInd: jmp $0000
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.segment "ZPSAVE"
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zpsave: .res zpspace
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.bss
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spsave: .res 1
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