Help me with hardware scrolling

c0burn · Post by **c0burn** » Fri Jan 26, 2024 11:13 pm

I am trying to draw a tile map (works great!) and next I want to play with moving it around by fiddling with r12/r13 of the CRTC, but just get screen corruption. I am obviously doing something silly, but what? Attached is the sprite data. This compiles in beebasm, targetting a Master with shadow/swram in Beebem, albeit the shadow stuff is commented out for now.

before i twiddle with r12/r13:

after i do so:

Code: Select all

; pointers to MOS
romsel = &FE30
osasci = &FFE3
oswrch = &FFEE
osbyte = &FFF4
oscli = &FFF7
romselcopy = &F4

; zero page addresses
addr = &70		; +71
screen = &72	; +73
counter1 = &74
counter2 = &75
counter3 = &76
counter4 = &77
xpos = &78
ypos = &79
counter5 = &80

; Code origin - PAGE is always E00 on a Master
ORG &E00

; Put a guard at the start of screen memory in mode 2
GUARD &3000

; Macros
MACRO VSYNC
	LDA #19:JSR osbyte
ENDMACRO

.mainstart
	; switch to mode 2 (shadow on - mode 130) (VDU 22,130)
    LDA #22:JSR oswrch
    ;LDA #130:JSR oswrch
	LDA #2:JSR oswrch
	
	; load our SWRAM into bank 4, by calling OSCLI with "command"
	LDX #LO(command)
	LDY #HI(command)
	JSR oscli
	
	; page in swram bank 4
	SEI:LDA #4:STA romselcopy:STA romsel:CLI
	
	; disable cursor (VDU 23,1,0,0,0,0,0,0,0,0)
	LDA #23:JSR oswrch
	LDA #1:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	
	; disable cursor editing (*FX 4,1)
	LDA #4:LDX #1:JSR osbyte

	; select main memory for VDU access (*FX 112,1)
	;LDA #112:LDX #1:JSR osbyte
	
	; clear screen (VDU 16)
    ;LDA #16:JSR oswrch
	;LDA #12:JSR oswrch

	; select main memory for display (*FX 113.1)
	;LDA #113:LDX #1:JSR osbyte
	
	; access shadow memory at &3000 (*FX 108,1)
	;LDA #108:LDX #1:JSR osbyte

;	LDA #1
;	LDX #4
;	LDY #6
;	JSR drawsprite
	
	LDA #69
	STA counter5
	LDA #18
	STA counter3
	LDA #24
	STA counter4
	.drawtiles
		.draw
			LDX counter5
			LDA map, X
			LDX counter3
			LDY counter4
			JSR drawsprite
			
			DEC counter5
			DEC counter3:DEC counter3
			BPL draw
			LDA #18
			STA counter3
		DEC counter4:DEC counter4:DEC counter4:DEC counter4
		BPL drawtiles


	LDA #23:JSR oswrch
	LDA #0:JSR oswrch
	LDA #12:JSR oswrch
	LDA #HI(&3280 DIV 8)
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch

	LDA #23:JSR oswrch
	LDA #0:JSR oswrch
	LDA #13:JSR oswrch
	LDA #LO(&3280 DIV 8)
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	LDA #0:JSR oswrch
	
;	LDA #0
;	STA counter3
;	LDA #12
;	STA counter4
	
;	.animate
;		LDX counter3
;		LDY counter4
;		JSR drawsprite
;		VSYNC
;
;		LDA counter3
;		CMP #18
;		BEQ end
;		
;		LDX counter3
;		LDY counter4
;		JSR drawtile
;		
;		LDA counter3
;		CLC
;		ADC #2
;		STA counter3
;		JMP animate
;	.end
	
	; select shadow memory for display (*FX 113,2)
	;LDA #113:LDX #2:JSR osbyte
RTS

.drawsprite ; pass A, X and Y
{
	STA counter2

	; number of sprite rows
	LDA #4
	STA counter1
	
	; position of sprite
	STX xpos
	STY ypos

	; get pointer to sprite
	LDA #LO(sprite)
	STA addr
	LDA #HI(sprite)
	STA addr+1
	
	LDY counter2
	LDA addr
	CLC
	ADC tileoffsetslo, Y
	STA addr
	
	LDY counter2
	LDA addr+1
	ADC tileoffsetshi, Y
	STA addr+1

	; draw 1/4 of the sprite
	.plotpixels
	{
		LDY ypos
		LDA loscreen,Y
		STA screen
		LDA hiscreen,Y
		STA screen+1
		
		LDX xpos
		LDA screen
		CLC
		ADC lox, X
		STA screen
		LDA screen+1
		ADC hix, X
		STA screen+1
	
		LDY #63
		.loop
			LDA (addr),Y
			STA (screen),Y
			DEY
			BPL loop
	}
	
	; increase the sprite pointer
	LDA addr
	CLC
	ADC #64
	STA addr
	LDA addr+1
	ADC #0
	STA addr+1
	
	; increase the screen row
	INC ypos
	
	; loop through rows
	DEC counter1
	BNE plotpixels
}
RTS

.drawtile ; pass X and Y registers
{
	; get pointer to sprite
	LDA #LO(sprite)
	STA addr
	LDA #HI(sprite)
	STA addr+1

	; number of sprite rows
	LDA #4
	STA counter1
	
	; position of sprite
	STX xpos
	STY ypos

	; draw 1/4 of the sprite
	.plotpixels
	{
		LDY ypos
		LDA loscreen,Y
		STA screen
		LDA hiscreen,Y
		STA screen+1
		
		LDX xpos
		LDA screen
		CLC
		ADC lox, X
		STA screen
		LDA screen+1
		ADC hix, X
		STA screen+1
	
		LDY #63
		.loop
			LDA (addr),Y
			STA (screen),Y
			DEY
			BPL loop
	}
	
	; increase the sprite pointer
	LDA addr
	CLC
	ADC #64
	STA addr
	LDA addr+1
	ADC #0
	STA addr+1
	
	; increase the screen row
	INC ypos
	
	; loop through rows
	DEC counter1
	BNE plotpixels
}
RTS

.hiscreen	EQUB &30, &32, &35, &37, &3A, &3C, &3F, &41, &44, &46, &49, &4B, &4E, &50, &53, &55, &58, &5A, &5D, &5F, &62, &64, &67, &69, &6C, &6E, &71, &73, &76, &78, &7B, &7D
.loscreen	EQUB &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80, &00, &80

.hix EQUB &00, &00, &00, &00, &00, &00, &00, &00, &01, &01, &01, &01, &01, &01, &01, &01, &02, &02, &02, &02
.lox EQUB &00, &20, &40, &60, &80, &A0, &C0, &E0, &00, &20, &40, &60, &80, &A0, &C0, &E0, &00, &20, &40, &60

.map 	EQUB	&00, &00, &00, &00, &00, &03, &00, &00, &00, &00
		EQUB	&00, &00, &00, &00, &00, &03, &00, &00, &00, &00
		EQUB	&00, &00, &00, &00, &00, &04, &01, &01, &01, &01
		EQUB	&00, &00, &00, &00, &00, &03, &00, &00, &00, &00
		EQUB	&01, &06, &01, &05, &01, &02, &00, &00, &00, &00
		EQUB	&00, &00, &00, &00, &00, &00, &00, &00, &00, &00
		EQUB	&00, &00, &00, &00, &00, &00, &00, &00, &00, &00

.tileoffsetslo	EQUB &00, &00, &00, &00, &00, &00, &00
.tileoffsetshi	EQUB &00, &01, &02, &03, &04, &05, &06

.command EQUS "SRLOAD SWRAM 8000 4", 13

.mainend
SAVE "Code", mainstart, mainend

; ********************
; SWRAM
; ********************

; start of sideways bank
ORG &8000

; guard end of bank
GUARD &C000

.swramstart

.sprite INCBIN "C:\Users\c0bur\Desktop\chips\sprites.bin"

.swramend
SAVE "SWRAM", swramstart, swramend

RobC · Post by **RobC** » Sat Jan 27, 2024 7:53 am

How are you manipulating the CRTC registers? And have you remembered to do the divide by 8 when setting the new screen address?

tricky · Post by **tricky** » Sat Jan 27, 2024 8:13 am

The second shot looks like the beginning of memory. Do you have R12 and r13 swapped?

You can also check what you have r12r13 set to in the debugger.

ChrisB · Post by **ChrisB** » Sat Jan 27, 2024 9:56 am

If this is your actual code you probably want to actually call oswrch instead of having a comment there....

Code: Select all

LDA #12:JSR oswrch
LDA #HI(&3280 DIV 8)
LDA #0:JSR oswrch

Edit: And if you have a new game in development we'd love to hear about it over in the new projects in development section.

c0burn · Post by **c0burn** » Sat Jan 27, 2024 9:58 am

I knew it was something stupid! Late night coding and a second pair of eyes was needed. Thank you!

c0burn · Post by **c0burn** » Sat Jan 27, 2024 10:09 am

ChrisB wrote: ↑Sat Jan 27, 2024 9:56 am Edit: And if you have a new game in development we'd love to hear about it over in the new projects in development section.

I will do so, but what you see is all of it so far - so less a game and more my first ever 6502 experiments.

lovebug · Post by **lovebug** » Sun Jan 28, 2024 4:46 pm

the experiment is looking great so far, keep up the good work

the graphics look interesting, I cant wait to see whats coming next

stardot.org.uk

Help me with hardware scrolling

Help me with hardware scrolling

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