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cc65/libsrc/atari/shadow_ram_prepare.s
Christian Groessler 478a7679a2 Force inclusion of 'shadow RAM preparation' load chunk in crt0.s and
not in the linker config file.
2013-10-18 22:08:26 +02:00

409 lines
9.5 KiB
ArmAsm

;
; Atari XL shadow RAM preparation routines
;
; Tasks:
; - move screen memory below load address
; - copy ROM chargen to its new place
; - copy shadow RAM contents to their destination
;
; Christian Groessler, chris@groessler.org, 2013
;
;DEBUG = 1
.ifdef __ATARIXL__
.export sramprep
.import __SRPREP_LOAD__, __SRPREPCHNK_LAST__
.import __SHADOW_RAM_LOAD__, __SHADOW_RAM_SIZE__, __SHADOW_RAM_RUN__
.import __SHADOW_RAM2_LOAD__, __SHADOW_RAM2_SIZE__, __SHADOW_RAM2_RUN__
.import __CHARGEN_START__, __CHARGEN_SIZE__
.import __STARTADDRESS__ ; needed by xlmemchk.inc
.include "zeropage.inc"
.include "atari.inc"
.include "save_area.inc"
.macro print_string text
.local start, cont
jmp cont
start: .byte text, ATEOL
cont: ldx #0 ; channel 0
lda #<start
sta ICBAL,x ; address
lda #>start
sta ICBAH,x
lda #<(cont - start)
sta ICBLL,x ; length
lda #>(cont - start)
sta ICBLH,x
lda #PUTCHR
sta ICCOM,x
jsr CIOV_org
.endmacro
; ------------------------------------------------------------------------
; EXE load chunk header
.segment "SRPREPHDR"
.word __SRPREP_LOAD__
.word __SRPREPCHNK_LAST__ - 1
; ------------------------------------------------------------------------
; Actual code
.segment "SRPREP"
; ***** entry point *****
sramprep:
.ifdef DEBUG
print_string "entering stage #2"
.endif
; save values of modified system variables and ports
lda RAMTOP
sta RAMTOP_save
lda MEMTOP
sta MEMTOP_save
lda MEMTOP+1
sta MEMTOP_save+1
lda APPMHI
sta APPMHI_save
lda APPMHI+1
sta APPMHI_save+1
lda PORTB
sta PORTB_save
; disable BASIC
lda PORTB
ora #2
sta PORTB
.include "xlmemchk.inc" ; calculate lowest address used and new value for RAMTOP
ldx lowadr
stx MEMTOP
lda lowadr+1
sta MEMTOP+1
lda lodadr+1
sta RAMTOP
; set APPMHI to MEMLO (+ 1 for sanity)
lda MEMLO
clc
adc #1
sta APPMHI
lda MEMLO+1
adc #0
sta APPMHI+1
; issue a GRAPHICS 0 call (copied'n'pasted from TGI drivers) to move screen memory down
jsr findfreeiocb
.ifdef DEBUG ; only check in debug version, this shouldn't really happen(tm)
beq iocbok
print_string "Internal error, no free IOCB!"
jsr delay
jsr delay
jsr delay
jsr restore ; restore stuff we've changed
jmp (DOSVEC) ; abort loading
iocbok:
.endif
; reopen it in Graphics 0
lda #OPEN
sta ICCOM,x
lda #OPNIN | OPNOT
sta ICAX1,x
lda #0
sta ICAX2,x
lda #<screen_device
sta ICBAL,x
lda #>screen_device
sta ICBAH,x
lda #<screen_device_length
sta ICBLL,x
lda #>screen_device_length
sta ICBLH,x
jsr CIOV_org
bpl scrok
; shouldn't happen(tm)
print_string "Internal error, aborting..."
jsr delay
jsr delay
jsr delay
jsr restore ; restore stuff we've changed
jmp (DOSVEC) ; abort loading
scrok: ; now close it again -- we don't need it anymore
lda #CLOSE
sta ICCOM,x
jsr CIOV_org
; copy chargen to low memory, just after the next possible address beyond our loaded chunk data
.ifdef DEBUG
print_string "copy chargen to low memory"
.endif
lda #>__SRPREPCHNK_LAST__
sta ptr3+1
lda #<__SRPREPCHNK_LAST__
sta ptr3
beq cg_addr_ok
; page align the new chargen address
inc ptr3+1
lda #0
sta ptr3
cg_addr_ok:
lda ptr3+1
and #3
beq cg_addr_ok2
; align to next 1K boundary
lda ptr3+1
and #$fc
clc
adc #4
sta ptr3+1
cg_addr_ok2:
lda #<DCSORG
sta ptr1
lda #>DCSORG
sta ptr1+1
lda ptr3
sta ptr2
lda ptr3+1
pha ; needed later to set CHBAS/CHBASE
sta ptr2+1
lda #>__CHARGEN_SIZE__
sta tmp2
lda #<__CHARGEN_SIZE__
sta tmp1
jsr memcopy
.ifdef DEBUG
print_string "now setting up high memory"
.endif
; disable ROM
sei
ldx #0
stx NMIEN ; disable NMI
lda PORTB
and #$fe
tax
pla ; get temp. chargen address
sta WSYNC ; wait for horiz. retrace
stx PORTB ; now ROM is mapped out
; switch to temporary chargen
sta CHBASE
sta CHBAS
; copy shadow RAM contents to their destination (segment SHADOW_RAM)
lda #<__SHADOW_RAM_SIZE__
bne do_copy
lda #>__SHADOW_RAM_SIZE__
beq no_copy ; we have no shadow RAM contents
; ptr1 - src; ptr2 - dest; tmp1, tmp2 - len
do_copy:lda #<__SHADOW_RAM_LOAD__
sta ptr1
lda #>__SHADOW_RAM_LOAD__
sta ptr1+1
lda #<__SHADOW_RAM_RUN__
sta ptr2
lda #>__SHADOW_RAM_RUN__
sta ptr2+1
lda #<__SHADOW_RAM_SIZE__
sta tmp1
lda #>__SHADOW_RAM_SIZE__
sta tmp2
jsr memcopy
no_copy:
; copy shadow RAM #2 contents to their destination (segment SHADOW_RAM2)
lda #<__SHADOW_RAM2_SIZE__
bne do_copy2
lda #>__SHADOW_RAM2_SIZE__
beq no_copy2 ; we have no shadow RAM #2 contents
; ptr1 - src; ptr2 - dest; tmp1, tmp2 - len
do_copy2:
lda #<__SHADOW_RAM2_LOAD__
sta ptr1
lda #>__SHADOW_RAM2_LOAD__
sta ptr1+1
lda #<__SHADOW_RAM2_RUN__
sta ptr2
lda #>__SHADOW_RAM2_RUN__
sta ptr2+1
lda #<__SHADOW_RAM2_SIZE__
sta tmp1
lda #>__SHADOW_RAM2_SIZE__
sta tmp2
jsr memcopy
no_copy2:
; copy chargen to its new (final) location
lda ptr3
sta ptr1
lda ptr3+1
sta ptr1+1
lda #<__CHARGEN_START__
sta ptr2
lda #>__CHARGEN_START__
sta ptr2+1
lda #>__CHARGEN_SIZE__
sta tmp2
lda #<__CHARGEN_SIZE__
sta tmp1
jsr memcopy
; re-enable ROM
lda PORTB
ora #1
ldx #>DCSORG
sta WSYNC ; wait for horiz. retrace
sta PORTB
stx CHBASE
stx CHBAS
lda #$40
sta NMIEN ; enable VB again
cli ; and enable IRQs
.ifdef DEBUG
print_string "Stage #2 OK"
print_string "loading main chunk"
jsr delay
.endif
rts
.include "findfreeiocb.inc"
; routine taken from http://www.obelisk.demon.co.uk/6502/algorithms.html
;
; copy memory
; ptr1 - source
; ptr2 - destination
; tmp2:tmp1 - len
.proc memcopy
ldy #0
ldx tmp2
beq last
pagecp: lda (ptr1),y
sta (ptr2),y
iny
bne pagecp
inc ptr1+1
inc ptr2+1
dex
bne pagecp
last: cpy tmp1
beq done
lda (ptr1),y
sta (ptr2),y
iny
bne last
done: rts
.endproc
; clean up after a fatal error
restore:lda RAMTOP_save
sta RAMTOP
lda MEMTOP_save
sta MEMTOP
lda MEMTOP_save+1
sta MEMTOP+1
lda APPMHI_save
sta APPMHI
lda APPMHI_save+1
sta APPMHI+1
rts
; short delay
.proc delay
lda #10
@loop: jsr delay1
clc
sbc #0
bne @loop
rts
delay1: ldx #0
ldy #0
@loop: dey
bne @loop
dex
bne @loop
rts
.endproc
.ifdef DEBUG
.byte "HERE ****************** HERE ***************>>>>>>"
sramsize:
.word __SHADOW_RAM_SIZE__
.endif ; .ifdef DEBUG
screen_device: .byte "S:",0
screen_device_length = * - screen_device
.ifdef DEBUG
.byte " ** srprep ** end-->"
.endif
; ------------------------------------------------------------------------
; Provide empty SHADOW_RAM and SHADOW_RAM2 segments in order that the
; linker is happy if the user program doesn't have these segments.
.segment "SHADOW_RAM"
.segment "SHADOW_RAM2"
; ------------------------------------------------------------------------
; EXE load chunk "trailer" - sets INITAD
.segment "SRPREPTRL"
.word INITAD
.word INITAD+1
.word sramprep
.endif ; .ifdef __ATARIXL__