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cc65/libsrc/atari/shadow_ram_prepare.s
2013-05-31 14:49:25 +02:00

346 lines
5.8 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
;
.if .defined(__ATARIXL__)
.export sramprep
.import __SRPREP_LOAD__, __SRPREP_SIZE__
.import __SHADOW_RAM_LOAD__, __SHADOW_RAM_SIZE__
.import __SHADOW_RAM_RUN__
.import __CHARGEN_START__, __CHARGEN_SIZE__
.import __SAVEAREA_LOAD__
.import zpsave
.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
; ------------------------------------------------------------------------
; Chunk header
.segment "SRPREPHDR"
.word __SRPREP_LOAD__
.word __SRPREP_LOAD__ + __SRPREP_SIZE__ + __SHADOW_RAM_SIZE__ - 1
; ------------------------------------------------------------------------
; Actual code
.segment "SRPREP"
sramprep:
print_string "in sramprep"
; 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
lda CIOV ; zero-page wrapper
sta ZP_CIOV_save
lda CIOV+1
sta ZP_CIOV_save+1
lda CIOV+2
sta ZP_CIOV_save+2
lda SIOV ; zero-page wrapper
sta ZP_SIOV_save
lda SIOV+1
sta ZP_SIOV_save+1
lda SIOV+2
sta ZP_SIOV_save+2
lda $fffe
sta IRQ_save
lda $ffff
sta IRQ_save+1
lda $fffc
sta RESET_save
lda $fffd
sta RESET_save+1
lda $fffa
sta NMI_save
lda $fffb
sta NMI_save+1
; disable BASIC
lda PORTB
ora #2
sta PORTB
; ... change system memory variables bla
CMPVAL = 64+255+992 ; you may ask, why these values... @@@ document
sys_ok: lda #<__SAVEAREA_LOAD__
sec
sbc #<CMPVAL
sta MEMTOP
sta APPMHI
lda #>__SAVEAREA_LOAD__
sbc #>CMPVAL
sta MEMTOP+1
sta APPMHI+1
lda #>__SAVEAREA_LOAD__ - 1
sta RAMTOP
; ... issue a GRAPHICS 0 call (copied'n'pasted from TGI drivers)
ldx #$50 ; take any IOCB, hopefully free (@@@ fixme)
; Reopen it in Graphics 0
lda #OPEN
sta ICCOM,x
lda #OPNIN | OPNOT
sta ICAX1,x
lda #0
sta ICAX2,x
lda #<screen_device
sta ICBAL,x
lda #>screen_device
sta ICBAH,x
lda #<screen_device_length
sta ICBLL,x
lda #>screen_device_length
sta ICBLH,x
jsr CIOV_org
bpl okoko
print_string "GR 0 FAILED"
jsr delay
jsr delay
jsr delay
jmp (DOSVEC) ; abort loading
okoko:
; Now close it again; we don't need it anymore :)
lda #CLOSE
sta ICCOM,x
jsr CIOV_org
print_string "GR 0 OKOKO"
jsr delay
; Save the zero page locations we need
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
; copy chargen to low memory
lda #>(__SRPREP_LOAD__ + __SRPREP_SIZE__ + __SHADOW_RAM_SIZE__)
sta ptr3+1
lda #<(__SRPREP_LOAD__ + __SRPREP_SIZE__ + __SHADOW_RAM_SIZE__)
sta ptr3
beq cg_addr_ok
; page align the new chargen address
inc ptr3+1
lda #0
sta ptr3
cg_addr_ok:
lda #<DCSORG
sta ptr1
lda #>DCSORG
sta ptr1+1
lda ptr3
sta ptr2
lda ptr3+1
sta ptr2+1
lda #>__CHARGEN_SIZE__
sta tmp2
lda #<__CHARGEN_SIZE__
sta tmp2+1
jsr memcopy
; TODO: switch to this temp. chargen
; disable ROMs
sei
ldx #0
stx NMIEN ; disable NMI
lda PORTB
and #$fe
sta PORTB ; now ROM is mapped out
; copy shadow RAM contents to their destination
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 chargen to its new 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
sta PORTB
lda #$40
sta NMIEN ; enable VB again
cli ; and enable IRQs
rts
; my 6502 fu is rusty, so I took a routine from the internet (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
.byte "HERE ****************** HERE ***************>>>>>>"
sramsize:
.word __SHADOW_RAM_SIZE__
; short delay
.proc delay
lda #10
l: jsr delay1
clc
sbc #0
bne l
rts
delay1: ldx #0
ldy #0
loop: dey
bne loop
dex
bne loop
rts
.endproc
screen_device: .byte "S:",0
screen_device_length = * - screen_device
.byte " ** srprep ** end-->"
; ------------------------------------------------------------------------
; Provide an empty SHADOW_RAM segment in order that the linker is happy
; if the user program doesn't have a SHADOW_RAM segment.
.segment "SHADOW_RAM"
; ------------------------------------------------------------------------
; Chunk "trailer" - sets INITAD
.segment "SRPREPTRL"
.word INITAD
.word INITAD+1
.word __SRPREP_LOAD__
.endif ; .if .defined(__ATARIXL__)