mirror of
https://github.com/cc65/cc65.git
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143 lines
2.5 KiB
ArmAsm
143 lines
2.5 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, callirq
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.import callmain, zerobss
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.import MEMTOP, RESTOR, BSOUT, CLRCH
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.import __INTERRUPTOR_COUNT__
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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 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 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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; 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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; Call 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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; 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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; Store the 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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; Back to BASIC
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rts
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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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