| | 8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
Howto flickerfree and moving rasterbar ?
<Post edited by moderator on 20/10-2009 01:24>
Making a perfect stable, flickerfree and moving rasterbar is harder than I thought.
Why and which changes are needed to the code below to fulfill my dream about the flickerfree rasterbar?
The code is based on http://www.ffd2.com/fridge/vic/stableraster.txt.
Acme code ready to compile:
!to "doubleirqrasterbar1.prg",cbm
*= $0800
!byte $00,$0c,$08,$0a,$00,$9e,$33,$32,$37,$36,$38,$00,$00,$00,$00
raspos = $00
maxpos = $7c
*= $8000 ;Assemble to $8000
cld ;Clear Decimal Mode
sei ;Disable IRQ's
lda #$1f ;Disable CIA IRQ's
sta $dc0d
sta $dd0d
; lda #<nmi ;Install NMI into
; ldx #>nmi ;Hardware NMI and
; sta $fffa ;RESET Vectors
; sta $fffc
; stx $fffb
; stx $fffd
lda #<irq1 ;Install RASTER IRQ
ldx #>irq1 ;into Hardware
sta $0314 ;Interrupt Vector
stx $0315
; lda #$35 ;Set MMU to RAM at
; ldx #$ff ;$a000-$bfff and
; sta $01 ;$e000-$ffff
; txs ;Clear the STACK
lda #$01 ;Enable RASTER IRQ
ldx #$1b ;High bit of RASTER
ldy #$34 ;compare register
sta $d01a ;and RASTER IRQ to
stx $d011 ;line $34
sty $d012
;NOTE double IRQ
;cannot be on or
;around a BAD LINE!
;(Fast Line)
lda #$0e ;Set Background
ldx #$06 ;and Border colors
ldy #$00 ;to default and
sta $d020 ;turn off sprites
stx $d021
sty $d015
jsr clrscreen
jsr clrcolor
; jsr printtext
asl $d019 ;Ack any previous
lda $dc0d ;IRQ's
lda $dd0d
cli ;Renable IRQ's
jmp * ;Endless Loop
irq1
sta reseta1 ;Preserve A,X and Y
stx resetx1 ;Registers
sty resety1 ;VIA self modifying
;code
;(Faster than the
;STACK is!)
lda #<irq2 ;Set IRQ Vector
ldx #>irq2 ;to point to the
ldy #$35 ;next part of the
sta $0314 ;Stable IRQ
stx $0315 ;ON NEXT LINE!
sty $d012
asl $d019 ;Ack RASTER IRQ
tsx ;We want the IRQ
cli ;To return to our
nop ;endless loop
nop ;NOT THE END OF
nop ;THIS IRQ!
nop
nop ;Execute nop's
nop ;until next RASTER
nop ;IRQ Triggers
nop
nop ;2 cycles per
nop ;instruction so
nop ;we will be within
nop ;1 cycle of RASTER
nop ;Register change
; nop ;<--- remove 1 NOP for PAL
irq2
txs ;Restore STACK
;Pointer
ldx #$08 ;Wait exactly 1
dex ;lines worth of
bne *-1 ;cycles for compare
bit $ea ;Minus compare
nop ;cycles
; nop ;<--- remove 1 NOP for PAL
lda #$35 ;RASTER change yet?
cmp $d012
beq start ;If no waste 1 more
;cycle
start
ldx raspos
cpx #maxpos
beq setrastup
inx
stx raspos
cpx #maxpos
bne rasterbarctrl
setrastup
ldx #$00
stx raspos ;Reset raster positon to
;zero if maximum has been reached.
rasterbarctrl
ldx raspos
ldy rastmov,x ;Wait for rasterline $3D-$96 at $D012
wait cpy $d012
bne wait
;rasterbar
ldx #$00
copy11 ldy rastime,x
dey
bne *-1
lda coloursr,x
sta $d020
sta $d021
inx
cpx #$10
bne copy11
lda #<irq3 ;Set IRQ to point
ldx #>irq3 ;to subsequent IRQ
ldy #$b8 ;at line $68
sta $0314
stx $0315
sty $d012
asl $d019 ;Ack RASTER IRQ
lda #$00 ;Reload A,X,and Y
reseta1 = *-1 ;registers
ldx #$00
resetx1 = *-1
ldy #$00
resety1 = *-1
; rti ;Return from IRQ
jmp $ea31
irq3
sta reseta2 ;Preserve A,X,and Y
stx resetx2 ;Registers
sty resety2
ldx #$0a ;Waste some more
dex ;time so effect
bne *-1 ;can be seen
nop
; lda #$0e ;More colors
; ldx #$06
; nop:nop
; sta $d021 ;Cool! subsequent
; stx $d021 ;IRQ's are also
;stable :-)
;Unless you are
;running realtime
;code :-)
ldy #$18 ;Waste time so this
dey ;IRQ does not try
bne *-1 ;to reoccur on the
;same line!
lda #<irq1 ;Reset Vectors to
ldx #>irq1 ;first IRQ again
ldy #$34 ;at line $34
sta $0314
stx $0315
sty $d012
asl $d019 ;Ack RASTER IRQ
lda #$00 ;Reload A,X,and Y
reseta2 = *-1 ;registers
ldx #$00
resetx2 = *-1
ldy #$00
resety2 = *-1
; rti ;Return from IRQ
jmp $ea81
;Pound RESTORE to
;get back to Turbo
nmi
asl $d019 ;Ack all IRQ's
lda $dc0d
lda $dd0d
lda #$81 ;reset CIA 1 IRQ
ldx #$00 ;remove raster IRQ
ldy #$37 ;reset MMU to roms
sta $dc0d
stx $d01a
sty $01
ldx #$ff ;clear the stack
txs
cli ;reenable IRQ's
jmp $9000 ;back to Turbo
clrscreen
lda #$20 ;Clear the screen
ldx #$00
clrscr sta $0400,x
sta $0500,x
sta $0600,x
sta $0700,x
dex
bne clrscr
rts
clrcolor
lda #$03 ;Clear color memory
ldx #$00
clrcol sta $d800,x
sta $d900,x
sta $da00,x
sta $db00,x
dex
bne clrcol
rts
printtext
lda #$16 ;C-set = lower case
sta $d018
ldx #$00
moretext lda text1,x
bpl lower ;upper case ?
eor #$80 ;yes
bne lower+2
lower and #$3f ;lower case
sta $0450,x
inx
cpx #$78
bne moretext
exit rts
text1
!scr "Stable Raster IRQ sourc"
!scr "e (PAL/NTSC) "
!scr "All Code by Fungus 1996"
!scr " "
!scr "Feel free to use and mo"
!scr "dify this code :)"
;------------------------------------------------------------------------------- -
;raster data
;------------------------------------------------------------------------------- -
rastime
!byte $08,$08,$08,$08,$08,$08,$08,$01
!byte $08,$08,$08,$08,$08,$08,$08,$01
coloursr
!byte $0b,$0b,$0c,$0c,$0f,$0f,$0d,$0d
!byte $0d,$0f,$0f,$0c,$0c,$0b,$0b,$00
rastmov
!byte $3D,$3D,$3E,$3E,$3F,$3F,$40,$40,$41,$42,$43,$44,$45,$46,$47,$48
!byte $49,$4A,$4C,$4E,$50,$52,$54,$56,$58,$5A,$5C,$5E,$60,$62,$64,$66
!byte $68,$6A,$6C,$6E,$70,$72,$74,$76,$78,$7A,$7C,$7E,$80,$82,$84,$86
!byte $88,$8A,$8C,$8E,$8F,$90,$91,$92,$93,$94,$94,$95,$95,$96,$96,$95
!byte $95,$94,$94,$93,$93,$92,$91,$90,$8F,$8E,$8D,$8D,$8B,$89,$87,$85
!byte $83,$81,$7F,$7D,$7B,$79,$77,$75,$73,$71,$6F,$6D,$6B,$69,$67,$65
!byte $63,$61,$5F,$5D,$5B,$59,$57,$55,$53,$51,$4F,$4D,$4B,$49,$48,$47
!byte $46,$45,$44,$43,$42,$41,$40,$40,$3F,$3F,$3E,$3E
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| | chatGPZ
Registered: Dec 2001
Posts: 11386 |
the "trick" is how you move the rasterbar. the basic idea is, unless you really know what you are doing (and why), then do NOT ever alter the position where the raster irq is triggered (ie, $d012). first make the basic routine stable (that should be easy enough with the example code you got there), then add simple rasterbars to it (which then should be stable and flickerfree). now to move stuff around, simply alter the table where the colors are taken from. (think of more advanced stuff like a dozen bars jumping up and down-how would you do that by altering $d012 in the first place... the table thing comes into mind again :))
|
| | Marauder/GSS
Account closed
Registered: Jul 2006
Posts: 224 |
if you want to move your *whole* color-bar/table up and down, then you could make your color-table bigger and just increase/decrease the pointer/start-positon where you're reading your colors from (-> lda coloursr,x)...
that way you don't have to alter the whole table and save some time... however works only if you don't want to have different color-bars jumping around... |
| | MagerValp
Registered: Dec 2001
Posts: 1078 |
The stable raster code that you started with (from the fridge) is timed for the hardware IRQ vector at $fffe, and you've changed the code to use the kernal IRQ vector at $0314. This fucks up the timing beyond repair. As others here not, you also can't move rastercode with $d012, as that also changes the timing. |
| | Skate
Registered: Jul 2003
Posts: 494 |
I agree with the guys above. Additionally moving $d012 is not that bad idea. But instead of self modifying code, I advice you to use zero page addresses holding raster positions.
Instead of
ldy #$34
sty $d012
...
...
...
ldy #$35
sty $d012
use
lda #$34
sta $a0 ; any available zeropage address is ok
ldy $a0
sty $d012
...
...
...
ldy $a0
iny
sty $d012
you should take care of cycle changes, adding removing some NOPs and BITs should be enough. After that to move the raster position just increase/decrease zeropage address ($a0 in this case) at the end of the frame. |
| | enthusi
Registered: May 2004
Posts: 677 |
you can switch off the screen (aka no badlines), then use stable raster and change $d012 but you probably dont want it this way.
|
| | 8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
Thanks for quick response !
Anyone that could rework the code and be the first to publish a fully stable and flicker free moving rasterbar routine ?
|
| | MagerValp
Registered: Dec 2001
Posts: 1078 |
No. We also won't do your homework, walk your dog, or call your grandma on her birthday.
|
| | 8bitforever
Account closed
Registered: Oct 2009
Posts: 48 |
MagerValp, the time has come for someone to finally
publish a stable, flickerfree moving rasterbar routine.
The demand for one is out there ;-)
This is what´s missing on the Internet and on the CSDB forum.
|
| | Moloch
Registered: Jan 2002
Posts: 2928 |
8bitforever - and you can be the one to do it! Do some studying and trial and error and be the first!
;)
|
| | SIDWAVE
Account closed
Registered: Apr 2002
Posts: 2238 |
Do a raster at line $xx, and then do this:
ldx #4 ;adjust this to remove flicker
.dex
bne .
ldx #0
..lda color,x
sta $d020
sta $d021
ldy timer,x
.dey
bne .
inx
bne ..
have it running in a monitor, and adjust the timer table to remove flicker.
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