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cc65/libsrc/apple2/crt0.s

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7.2 KiB
ArmAsm
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;
; Startup code for cc65 (Apple2 version)
;
; This must be the *first* file on the linker command line
;
.export _exit
.import zerobss
.import initlib, donelib
.import callmain, callirq
.import __RAM_START__ , __RAM_LAST__ ; Linker generated
.import __MOVE_START__, __MOVE_LAST__ ; Linker generated
.import __LC_START__ , __LC_LAST__ ; Linker generated
.import __BSS_RUN__ , __INIT_SIZE__ ; Linker generated
.import __INTERRUPTOR_COUNT__ ; Linker generated
.include "zeropage.inc"
.include "apple2.inc"
.linecont +
; ------------------------------------------------------------------------
.segment "EXEHDR"
.addr __RAM_START__ ; Start address
.word __BSS_RUN__ - __RAM_START__ + \
__MOVE_LAST__ - __MOVE_START__ ; Size
; ------------------------------------------------------------------------
.segment "STARTUP"
; ProDOS TechRefMan, chapter 5.2.1:
; "For maximum interrupt efficiency, a system program should not
; use more than the upper 3/4 of the stack."
ldx #$FF
txs ; Init stack pointer
; Switch in LC bank 2 for W/O
bit $C081
bit $C081
; Set source start address
lda #<(__BSS_RUN__ + __INIT_SIZE__)
ldy #>(__BSS_RUN__ + __INIT_SIZE__)
sta $9B
sty $9C
; Set source last address
lda #<(__BSS_RUN__ + __INIT_SIZE__ + __LC_LAST__ - __LC_START__)
ldy #>(__BSS_RUN__ + __INIT_SIZE__ + __LC_LAST__ - __LC_START__)
sta $96
sty $97
; Set destination last address
lda #<__LC_LAST__
ldy #>__LC_LAST__
sta $94
sty $95
; Call into Applesoft Block Transfer Utility - which handles zero
; sized blocks well - to move content of the LC memory area
jsr $D396 ; BLTU + 3
; Set source start address
lda #<__BSS_RUN__
ldy #>__BSS_RUN__
sta $9B
sty $9C
; Set source last address
lda #<(__BSS_RUN__ + __INIT_SIZE__)
ldy #>(__BSS_RUN__ + __INIT_SIZE__)
sta $96
sty $97
; Set destination last address
lda #<__RAM_LAST__
ldy #>__RAM_LAST__
sta $94
sty $95
; Call into Applesoft Block Transfer Utility - which handles moving
; overlapping blocks upwards well - to move the INIT segment
jsr $D396 ; BLTU + 3
; Delegate all further processing to keep the STARTUP segment small
jsr init
; Avoid re-entrance of donelib. This is also the _exit entry
_exit: ldx #<exit
lda #>exit
jsr reset ; Setup RESET vector
; Switch in ROM in case it wasn't already switched in by a RESET
bit $C082
; Call module destructors
jsr donelib
; Check for valid interrupt vector table entry number
lda intnum
beq exit
; Deallocate interrupt vector table entry
dec params ; Adjust parameter count
jsr $BF00 ; MLI call entry point
.byte $41 ; Dealloc interrupt
.addr params
; Restore the original RESET vector
exit: ldx #$02
: lda rvsave,x
sta SOFTEV,x
dex
bpl :-
; Copy back the zero page stuff
ldx #zpspace-1
: lda zpsave,x
sta sp,x
dex
bpl :-
; ProDOS TechRefMan, chapter 5.2.1:
; "System programs should set the stack pointer to $FF at the
; warm-start entry point."
ldx #$FF
txs ; Re-init stack pointer
; Back to DOS
jmp DOSWARM
; ------------------------------------------------------------------------
.segment "INIT"
; Save the zero page locations we need
init: ldx #zpspace-1
: lda sp,x
sta zpsave,x
dex
bpl :-
; Clear the BSS data
jsr zerobss
; Save the original RESET vector
ldx #$02
: lda SOFTEV,x
sta rvsave,x
dex
bpl :-
; ProDOS TechRefMan, chapter 5.3.5:
; "Your system program should place in the RESET vector the
; address of a routine that ... closes the files."
ldx #<_exit
lda #>_exit
jsr reset ; Setup RESET vector
; Setup the stack
lda HIMEM
sta sp
lda HIMEM+1
sta sp+1 ; Set argument stack ptr
; Check for interruptors
lda #<__INTERRUPTOR_COUNT__
beq :+
; Check for ProDOS
lda $BF00 ; MLI call entry point
cmp #$4C ; Is MLI present? (JMP opcode)
bne prterr
; Allocate interrupt vector table entry
jsr $BF00 ; MLI call entry point
.byte $40 ; Alloc interrupt
.addr params
bcs prterr
; Enable interrupts as old ProDOS versions (i.e. 1.1.1)
; jump to SYS and BIN programs with interrupts disabled
cli
; Call module constructors
: jsr initlib
; Switch in LC bank 2 for R/O
bit $C080
; Push arguments and call main()
jmp callmain
; Print error message and return
prterr: ldx #msglen-1
: lda errmsg,x
jsr $FDED ; COUT
dex
bpl :-
rts
errmsg: .ifdef __APPLE2ENH__
.byte $8D, 't'|$80, 'p'|$80, 'u'|$80, 'r'|$80, 'r'|$80
.byte 'e'|$80, 't'|$80, 'n'|$80, 'i'|$80, ' '|$80, 'c'|$80
.byte 'o'|$80, 'l'|$80, 'l'|$80, 'a'|$80, ' '|$80, 'o'|$80
.byte 't'|$80, ' '|$80, 'd'|$80, 'e'|$80, 'l'|$80, 'i'|$80
.byte 'a'|$80, 'F'|$80, $8D
.else
.byte $8D, 'T'|$80, 'P'|$80, 'U'|$80, 'R'|$80, 'R'|$80
.byte 'E'|$80, 'T'|$80, 'N'|$80, 'I'|$80, ' '|$80, 'C'|$80
.byte 'O'|$80, 'L'|$80, 'L'|$80, 'A'|$80, ' '|$80, 'O'|$80
.byte 'T'|$80, ' '|$80, 'D'|$80, 'E'|$80, 'L'|$80, 'I'|$80
.byte 'A'|$80, 'F'|$80, $8D
.endif
msglen = * - errmsg
; ------------------------------------------------------------------------
.segment "LOWCODE"
; ProDOS TechRefMan, chapter 6.2:
; "Each installed routine must begin with a CLD instruction."
intrpt: cld
; Call interruptors and check for success
jsr callirq
bcc :+
; ProDOS TechRefMan, chapter 6.2:
; "When the routine that can process the interrupt is called, it
; should ... return (via an RTS) with the carry flag clear."
clc
rts
; ProDOS TechRefMan, chapter 6.2:
; "When a routine that cannot process the interrupt is called,
; it should return (via an RTS) with the cary flag set ..."
: sec
rts
; Setup RESET vector
reset: stx SOFTEV
sta SOFTEV+1
eor #$A5
sta PWREDUP
rts
; ------------------------------------------------------------------------
.data
zpsave: .res zpspace
params: .byte $02 ; Parameter count
intnum: .byte $00 ; Interrupt number
.addr intrpt ; Interrupt handler
; ------------------------------------------------------------------------
.bss
rvsave: .res 3