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Hi all,

I write music for SMS/GG, using both VGM (generating files containing PSG/YM2413 information) and by assembler (TASM). The documentation is excellent, still would like ask an advice or preferably short code snippet for an accurate timer. As I only do music, there's no need for any graphics, code may start straightly from .org $1000 or with some short initialization, after that I just load stuff to accumulator and output them correct addresses ($7F, $F0,$F1).
So I would need a short accurate code snippet for delay, something very simple that I haven't found so far. Each program is for one use only, generating source material for a composition (or in some cases being the composition itself), recorded and then I start a new program for next composition. Pure chip programming, not trying to do melodies etc., it is like a series of sound effects, usually in endless loop.

Any advices are highly appreciated !

Best,
Jukka

If you're not going to set up a proper VBlank setup then you can do something like:

WaitForVBlank:
-: in a,($bf)
and $80
jr z,-
ret

(untested, remember to disable interrupts)

Alternative: http://www.smspower.org/forums/viewtopic.php?p=36883#36883

EDIT: Seems emulator problem, I tried first with Dega, stucks to the first sound, now tried with Meka too and works perfectly there ! Thanks Maxim.

-J

Excellent, thanks Maxim, exactly what I was looking for (I've used simple VBlank with other consoles too). I copied the code, TASM didn't liked -: label, so I changed it, after setting the YM2413 registers I call the WaitForVBlank,
but it seems to stuck there, to the first sound. I disabled interrupts simply by

.org $0000
di
.org $1000
jp Main
Main:

;start loading register values to chip
call WaitForVBlank

;rest of the code (loading more values and calling WaitForVBlank after each chip setting)

Just using one call WaitForVBlank in testing, afterwards I will use a loop with it.
Anyway it stucks to the first sound, any tips ?

Thanks !

-Jukka

Maxim wrote

If you're not going to set up a proper VBlank setup then you can do something like:

WaitForVBlank:
-: in a,($bf)
and $80
jr z,-
ret

(untested, remember to disable interrupts)

Alternative: http://www.smspower.org/forums/viewtopic.php?p=36883#36883

Author	Message
jp48 Joined: 19 May 2010 Posts: 17 Location: Finland	SMS, simple timer/delay for music Posted: Thu Jul 08, 2010 8:33 am
jp48 Joined: 19 May 2010 Posts: 17 Location: Finland	Hi all, I write music for SMS/GG, using both VGM (generating files containing PSG/YM2413 information) and by assembler (TASM). The documentation is excellent, still would like ask an advice or preferably short code snippet for an accurate timer. As I only do music, there's no need for any graphics, code may start straightly from .org $1000 or with some short initialization, after that I just load stuff to accumulator and output them correct addresses ($7F, $F0,$F1). So I would need a short accurate code snippet for delay, something very simple that I haven't found so far. Each program is for one use only, generating source material for a composition (or in some cases being the composition itself), recorded and then I start a new program for next composition. Pure chip programming, not trying to do melodies etc., it is like a series of sound effects, usually in endless loop. Any advices are highly appreciated ! Best, Jukka

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	Posted: Thu Jul 08, 2010 9:34 am
	If you're not going to set up a proper VBlank setup then you can do something like: WaitForVBlank: -: in a,($bf) and $80 jr z,- ret (untested, remember to disable interrupts) Alternative: http://www.smspower.org/forums/viewtopic.php?p=36883#36883

jp48 Joined: 19 May 2010 Posts: 17 Location: Finland	Posted: Thu Jul 08, 2010 10:12 am
jp48 Joined: 19 May 2010 Posts: 17 Location: Finland	EDIT: Seems emulator problem, I tried first with Dega, stucks to the first sound, now tried with Meka too and works perfectly there ! Thanks Maxim. -J Excellent, thanks Maxim, exactly what I was looking for (I've used simple VBlank with other consoles too). I copied the code, TASM didn't liked -: label, so I changed it, after setting the YM2413 registers I call the WaitForVBlank, but it seems to stuck there, to the first sound. I disabled interrupts simply by .org $0000 di .org $1000 jp Main Main: ;start loading register values to chip call WaitForVBlank ;rest of the code (loading more values and calling WaitForVBlank after each chip setting) Just using one call WaitForVBlank in testing, afterwards I will use a loop with it. Anyway it stucks to the first sound, any tips ? Thanks ! -Jukka Maxim wrote If you're not going to set up a proper VBlank setup then you can do something like: WaitForVBlank: -: in a,($bf) and $80 jr z,- ret (untested, remember to disable interrupts) Alternative: http://www.smspower.org/forums/viewtopic.php?p=36883#36883

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