Centiseconds in Sonic 1

Okay, this isn't a big thing for my hack Soniquest, but I've always wanted to insert the milliseconds feature that used in most projects nowadays into my hack.


As of now, my asm is loading the data, but it's just not showing up correctly on the screen (in the HUD). Instead, it appears in objects, more specifically the starposts.





Wasn't the ASM code for this once available to the public? And if you want to see my coding:

Code:

Hud_ChkTime:

		tst.b	($FFFFFE1E).w	; does the time	need updating?

		beq.w	Hud_ChkLives	; if not, branch

		tst.w	($FFFFF63A).w	; is the game paused?

		bne.w	Hud_ChkLives	; if yes, branch

		lea	($FFFFFE22).w,a1

		cmpi.l	#$93B3B,(a1)+	; is the time 9.59?

		beq.w	TimeOver	; if yes, branch

		addq.b	#1,-(a1)

		jsr	Miliseconds

		cmpi.b	#$3C,(a1)

		bcs.w	Hud_ChkLives

		move.b	#0,(a1)

		addq.b	#1,-(a1)

		cmpi.b	#$3C,(a1)

		bcs.s	loc_1C734

		move.b	#0,(a1)

		addq.b	#1,-(a1)

		cmpi.b	#9,(a1)

		bcs.s	loc_1C734

		move.b	#9,(a1)

		bra loc_1c734

		

Miliseconds:

		move.l	a1,-(sp)

		moveq	#0,d0

		moveq	#0,d1

		move.b	($FFFFFE25).w,d1

		move.b	d1,d0
		divu.w	#3,d0
		mulu.w	#2,d0
		add.b	d0,d1
		sub.w	#1,d1
		bpl   Negativenum
		move.w	#0,d1

Negativenum:
		cmp.w	#100,d1
		blo.w	Hundrednum
		move.w	#99,d1

Hundrednum:
		cmp.b	#3,($FFFFFE25).w
		bne     Secnum
		move.w	#5,d1

Secnum:
		move.l	#$73E00003,d0
		jsr	Hud_Secs
		move.l	(sp)+,a1
		rts

I have no clue what I'm supposed to do Hud_Secs subroutine, or where to go from here.

 

I modified the topic title. You're after centiseconds, I believe. If you're trying to go for what Megamix and The Lost Land have for timers, then yes, it's centiseconds... not milliseconds.


Centiseconds: xx'yy"zz


Milliseconds: xx'yy"zzz


In regards to the routine, I could just pass you my source, but then again, I didn't make it possible for it to be in my hack. Stephen and Ordos (I think) did.

 

Well, I actually did want milliseconds. But I figured the coding from Megamix and Lost Land could add the additional number into the HUD. It shouldn't be too hard, but I think I screwed up somewhere in my ASM.

 

This is a pretty simple one. There's two steps involved.


First off, see this line?

Code:

move.l #$73E00003,d0

That's a VDP instruction. In this context, what you need to know is that it's setting the destination in VRAM for the numbers to be dynamically reloaded. The parts you want to edit are the first 3 nybbles, or $73E. This is the tile offset in VRAM that the tiles are being loaded to--to convert this value to a VRAM address, multiply it by $20.


Once you pick the VRAM address you want, divide the value by $20 and replace those 3 nybbles with it. After that, you simply need to edit the HUD mappings to read from that VRAM address in order to display the centisecond counter. You could ask Shadow Fire for help in that regard if you don't know what to do, but otherwise that should be all you need to know.