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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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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: 680 |
already discussed here a couple years ago detecting pal, drean, ntsc or old ntsc |
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Sokrates
Registered: Jun 2014
Posts: 7 |
Quote: The module version of Spike+Minestorm have a drean detection and support it, also Jars Revenge ...
Could you elaborate on that please? Maybe in a new thread "extra features in games/demos for drean" or so? |
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Peiselulli
Registered: Oct 2006
Posts: 81 |
"support" only means that my (typical) CIA timers are adjusted if the different machines are detected, so the games will work. No more, no less. |
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Silver Dream !
Registered: Nov 2005
Posts: 108 |
FYI - added a different approach to codebase64 a few days ago. Can save some bytes in specific situations.
http://codebase64.org/doku.php?id=base:efficient_tod_initialisa.. |
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TWW
Registered: Jul 2009
Posts: 545 |
Interesting.
This is the way I detect the frequency (after determining the model):
// Detect AC Frequency
// ===================
// PAL TEST 50Hz: #$7f
// PAL TEST 60Hz: #$32
// NTSC TEST 50Hz: #$b3
// NTSC TEST 60Hz: #$70
// NTSC2 TEST 50Hz: #$b3
// NTSC2 TEST 60Hz: #$70
// DREAN TEST 50Hz: #$70
// DREAN TEST 60Hz: #$20
DetectACFrequency:
lda #$ff
sta $dc04
sta $dc05 // CIA #1 Timer A = #$ffff
sta $dc06
sta $dc07 // CIA #1 Timer B = #$ffff
lda #$00
sta $dc0b
sta $dc0a
sta $dc09
sta $dc08 // CIA #1 TOD set to 00:00:00:00
ldx #%10000001 // CIA #1 Timer A Start + TOD = 50 Hz
lda VideoSystem
beq !+ // Branch if PAL (use 50Hz)
cmp #$03
beq !+ // Branch if DREAN (use 50Hz)
ldx #%00000001 // CIA #1 Timer A Start + TOD = 60 Hz (NTSC/NTSC2)
!: ldy #%01000001 // CIA #1 Timer B Start + Sync with Timer A
lda $dc08
!: cmp $dc08
beq !- // Wait untill TOD changes with 1/10 second
stx $dc0e // CIA #1 Timer A Start
sty $dc0f // CIA #1 Timer B Start
lda $dc08
!: cmp $dc08
beq !- // Wait untill TOD changes with 1/10 second
lda $dc05
ldx VideoSystem
beq PALorDREAN
cpx #$03
beq PALorDREAN
NTSCorNTSC2:
cmp Table50Hz,x
bne TOD50Hz
jmp TOD60Hz
PALorDREAN:
cmp Table50Hz,x
bne TOD60Hz
TOD50Hz:
lda #$81
ldx #$80
ldy #50
jmp !+
TOD60Hz:
lda #$01
ldx #$00
ldy #60
!: sta $dc0e
stx $dd0e // Set correct frequency on TOD Clocks and initialize CIA #1 & #2 Control Register A
sty ACMains
rts
//---------------------------------------------------------------------
// DATA: 50/60 Hz Detection Table
//
// PAL/50 - #$fffe 7f 28 - 98.519 cycles => MPU Clock = 0,985 MHz
// PAL/60 - #$fffe 32 24 - 118.235 cycles
//
// NTSC/50 - #$fffe b3 0f - 85.232 cycles
// NTSC/60 - #$fffe 70 7d - 102.274 cycles => MPU Clock = 1,023 MHz
//
// NTSC2/50 - #$fffe b3 12 - 85.229 cycles
// NTSC2/60 - #$fffe 70 6b - 102.292 cycles => MPU Clock = 1,023 MHz
//
// DREAN/50 - #$fffe 70 23 - 102.326 cycles => MPU Clock = 1,023 MHz
// DREAN/60 - #$fffe 20 32 - 122.829 cycles
Table50Hz: // Values to detect that
.byte $7f // PAL
.byte $70 // NTSC_OLD
.byte $70 // NTSC
.byte $70 // DREAN
Works in all configs of vice using a regular C64 but that 'could' be missguiding ,-) |
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Silver Dream !
Registered: Nov 2005
Posts: 108 |
I basically needed simple way to properly initialise TOD. Being lazy I had a look at what was available on codebase but found only something I wouldn't want to use for a few reasons. Therefore I fired up a spreadsheet, calculated what was needed and wrote my own. Once done, adding only two CMPs looked like a no-brainer. |
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TWW
Registered: Jul 2009
Posts: 545 |
Do please share 8-) |
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Krill
Registered: Apr 2002
Posts: 2969 |
I'm not sure i understand. The aim is to detect the mains frequency regardless of the computer's native video mode? E.g.., be able to detect a PAL C-64 running in NTSC land and vice versa, for some reason? Why? :) |
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