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Dr. Jay
Account closed
Registered: Jan 2003
Posts: 32 |
PAL/NTSC detect
Just wanted to share a quick routine that detects PAL/NTSC WITHOUT using interrupts or latches.
;pal/NTSC detect - 0 = PAL, non-zero = NTSC
palntsc
sei ; disable interrupts
wait
lda $d012
bne wait ; wait for rasterline 0 or 256
wait1
lda $d011 ; Is rasterbeam in the area
bpl wait1 ; 0-255? if yes, wait
wait2
ldy #$00
synch1 lda $d012
cmp #$37 ; top PAL rasterline
bne synch1
lda $d012 ; if next is 0, then PAL
synch2 cmp $d012
beq synch2
lda $d012
cli ; enable interrupts
rts ; return
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
BCC should have been BMI
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Frantic
Registered: Mar 2003
Posts: 1629 |
I added TLR's and Graham's routines to codebase (the PAL/NTSC detect page) (and changed bcc to bmi).
//FTC |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
Slight improvement would be:
w0 LDA $D012
w1 CMP $D012
BEQ w1
BMI w0
AND #$03
#$03 -> 312 rasterlines
#$02 -> 263 rasterlines
#$01 -> 262 rasterlines
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Moloch
Registered: Jan 2002
Posts: 2896 |
Ancient thread brought back to life, but certainly some excellent examples recently posted. Will work nicely for my NTSC/PAL detection needs, thanks!
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Sokrates
Registered: Jun 2014
Posts: 7 |
Enhanced version to differ between PAL and PAL-N. First count rasterlines, then count cycles.
LDX #$00
w0 LDA $D012
w1 CMP $D012
BEQ w1
BMI w0
AND #$03
CMP #$03
BNE detectionDone ; done for NTSC
TAY
countCycles
INX
LDA $D012
BPL countCycles
CPX #$5E ; VICE values: PAL-N=$6C PAL=$50
; so choose middle value $5E for check
BCC isPAL
INY ; is PAL-N
isPAL
TYA
detectionDone
...
Results in the accumulator:
#$01: 262 rasterlines and 64 cycles per line [NTSC: 6567R56A VIC] (OLD NTSC)
#$02: 263 rasterlines and 65 cycles per line [NTSC: 6567R8 VIC]
#$03: 312 rasterlines and 63 cycles per line [PAL: 6569 VIC]
#$04: 312 rasterlines and 65 cycles per line [Drean PAL-N: 6572 VIC] |
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Count Zero
Registered: Jan 2003
Posts: 1825 |
Saw your edit on codebase - thanks for that!
Wonder whenever some special fix becomes drean-only or such. Those few more cycles likely only add advantage on calculations for some games, hm? |
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TWW
Registered: Jul 2009
Posts: 541 |
Another version:
.pseudocommand VSync {
bit $d011
bpl *-3
bit $d011
bmi *-3
}
lda #$ff
sta $dc04
sta $dc05 // Latch #$ffff to Timer A
:VSync
ldx #%00011001
stx $dc0e // Start Timer A (One shot mode (Timer stops automatically when underflow))
:VSync
sec
sbc $dc05 // Hibyte number of counter
and #%00000011
A now contains the video system as follows:
#0 - NTSC1
#1 - DREAN
#2 - PAL
#3 - NTSC2
Edit: Rectified bug. |
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Sokrates
Registered: Jun 2014
Posts: 7 |
Quote: Saw your edit on codebase - thanks for that!
Wonder whenever some special fix becomes drean-only or such. Those few more cycles likely only add advantage on calculations for some games, hm?
Does anyone know about games/demos using the extra cycles of the drean?
My interest was only to have stable rasterlines for all VIC types. Just to be complete.
@TWW: I found your webpage about this topic after you post :-) |
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Peiselulli
Registered: Oct 2006
Posts: 81 |
The module version of Spike+Minestorm have a drean detection and support it, also Jars Revenge ... |
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Fungus
Registered: Sep 2002
Posts: 628 |
already discussed here a couple years ago detecting pal, drean, ntsc or old ntsc |
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