; collision demonstration for the G7000 by Soeren Gust
; Version 1.3

; $Id: collision.a48 390 2003-07-19 12:41:28Z sgust $

; History:
; Version 1.3
;   The hextable was wrong, D and E were swapped.
;
; Version 1.2
;   Removed unnecessary call vdcenable at beginning.
;
; Version 1.1
;   moved display of collision register, now visible on o2em
;
; Version 1.0
;   first release
;
; This program demonstrates how to check for collisions and how to play one
; of the builtin sound tunes.

; Copyright (C) 1997-2002 by Soeren Gust, sgust@ithh.informationstheater.de

; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

; You can always get the latest version at http://soeren.informationstheater.de

	cpu	8048

; some variables in internal ram

iram_xl		equ	020h		; bit 0-7 of x position
iram_xh		equ	021h		; bit 8 of y position
iram_y		equ	022h		; y position
iram_colctrl	equ	023h		; color/control

	org	400h
	
	include	"g7000.h"

	jmp	selectgame	; RESET
	jmp	irq		; interrupt
	jmp	timer		; timer
	jmp	vsyncirq	; VSYNC-interrupt
	jmp	start		; after selectgame
	jmp	soundirq	; sound-interrupt

timer	retr			; we don't need timer

start
	call	gfxoff

	; initialise sprite shapes
	mov	r0,#vdc_spr0_shape
	mov	r1,#spriteball & 0ffh
	call	setshape

	mov	r0,#vdc_spr1_shape
	mov	r1,#spritetriangle & 0ffh
	call	setshape

	; set sprite position for triangle
	mov	r0,#vdc_spr1_ctrl
	mov	a,#01Ch		; y position
	movx	@r0,a
	inc	r0
	mov	a,#01Ch		; x position
	movx	@r0,a
	inc	r0
	mov	a,#col_spr_red
	movx	@r0,a

	; set colors
	mov	r0,#vdc_color
	mov	a,#col_grd_blue
	movx	@r0,a

	; set grid
	mov	r0,#vdc_gridv1
	mov	a,#001h
	movx	@r0,a

	mov	r0,#vdc_gridh0
	mov	a,#002h
	movx	@r0,a

	mov	r0,#vdc_gridh1
	mov	a,#002h
	movx	@r0,a

	; set char
	mov	r0,#vdc_char2
	mov	r3,#00Eh	; x position
	mov	r4,#01Fh	; y position
	mov	r5,#03Ch	; ship1
	mov	r6,#col_chr_green
	call	printchar

	call	gfxon		; turn gfx on

	; initialise internal variables
	mov	r0,#iram_xl
	mov	a,#02Ah
	mov	@r0,a
	mov	r0,#iram_xh
	mov	a,#0
	mov	@r0,a
	mov	r0,#iram_y
	mov	a,#038h
	mov	@r0,a
	mov	r0,#iram_colctrl
	mov	a,#col_spr_white
	mov	@r0,a

loop
	call	waitvsync	; wait for begin of frame

	call	vdcenable	; enable vdc

	; tell the vdc to look for collisions with sprite 0
	; in the next frame
	mov	r0,#vdc_collision
	mov	a,#vdc_coll_spr0
	movx	@r0,a		; activate collision checks

	; display the contents of the collision register on
	; the right side. this information reflects the
	; situation of the last frame.
	call	gfxoff
	mov	r0,#iram_collision
	mov	a,@r0
	mov	r0,#vdc_char0
	mov	r3,#040h	; x position
	mov	r4,#01Eh	; y position
	mov	r6,#col_chr_white
	call	displayhex
	call	gfxon

	mov	r1,#0		; joystick 0
	call	getjoystick	; get offsets

	cpl	F0
	jf0	nofire		; skip next part
				; if not fire

	; start playing the builtin tune for "explode" 
	; the rest is done by the irq routines in rom
	mov	a,#tune_explode
	call	playsound

nofire
	call	extramenable	; enable extram
	mov	r0,#07fh	; start of table

setpos
	; adjust sprite positions in iram
	; y is simple
	mov	r1,#iram_y	; y position
	mov	a,@r1		; get it
	add	a,r3		; add offset
	mov	@r1,a		; store y postion

	; x is a 9 bit add using carry, we need to expand r2 to 9 bit also
	mov	r1,#iram_xl	; low byte of x
	mov	a,@r1		; get it
	add	a,r2		; add offset, sets carry if necessary
	mov	@r1,a		; store low byte of x
	mov	r1,#iram_xh	; high bit of x
	mov	a,@r1		; get it
	addc	a,#0		; add the carry
	mov	r7,a		; we need this later
	mov	a,r2		; get offset
	rr	a		; reuse bit 1 of offset as bit 8
				; we need it, because we are dealing with
				; 2s complement if R2=-1=01ffh
	add	a,r7		; add result from above to bit 8 of offset
	anl	a,#001h		; we only need 1 bit
	mov	@r1,a		; store it as high bit

	; prepare table for sprite positions
	mov	a,#3		; copy 3 bytes
	movx	@r0,a
	dec	r0
	mov	a,#vdc_spr0_ctrl
	movx	@r0,a
	dec	r0

	; set sprite positions from iram using table
	mov	r1,#iram_y	; y position
	mov	a,@r1		; get it
	movx	@r0,a		; put it into table
	dec	r0

	; x position: recombine xh and xl and split it into 8-1/0
	mov	r1,#iram_xh	; highest bit of x position
	mov	a,@r1
	rrc	a		; highest bit of sprite_x into carry
	mov	r1,#iram_xl	; low byte of x positon
	mov	a,@r1
	rrc	a		; lowest bit into carry, highest bit into 7
	movx	@r0,a		; put bit 8-1 of sprite_x into sprite control 1
	dec	r0
	mov	a,#0		; we only need carry (lowest bit of sprite_x)
	rlc	a		; lowest bit of sprite_x into bit 0
	mov	r7,a		; store in r7
	mov	r1,#iram_colctrl; color/control
	mov	a,@r1		; get it
	orl	a,r7		; put it together
	movx	@r0,a		; put it into sprite control 2 via table
	dec	r0

	call	tableend	; thats all

	jmp	loop


; start a new page, only to make sure that shapes and the code which
; accesses them are in one page, same for displayhex and hextable

	align	256

	; the shapes of the sprites
	; the images are mirrored on the y axis
spriteball:
	db	00111100b
	db	01111110b
	db	11111111b
	db	11111111b
	db	11111111b
	db	11111111b
	db	01111110b
	db	00111100b

spritetriangle:
	db	00000001b
	db	00000011b
	db	00000111b
	db	00001111b
	db	00011111b
	db	00111111b
	db	01111111b
	db	11111111b

setshape
; r0=spritepointer, r1=pointer to image in rom
	mov	r7,#8		; 8 bytes
copyspriteloop:
	mov	a,r1
	movp	a,@a		; get byte
	movx	@r0,a
	inc	r0
	inc	r1
	djnz	r7,copyspriteloop

	ret

displayhex
; r0=charpointer r3=x, r4=y, r6=color a=number
; alters r7
	mov	r7,a
	swap	a
	anl	a,#00fh
	call	displayhexnibble
	mov	a,r7
	anl	a,#00fh
	call	displayhexnibble
	ret

displayhexnibble
; r0=charpointer r3=x, r4=y, r6=color, a=number
; alters r3, r5, a
	add	a,#hextable & 0ffh
	movp	a,@a
	mov	r5,a
	call	printchar
	ret

hextable:
	db	0,1,2,3,4,5,6,7,8,9,020h,025h,023h,01ah,012h,01bh

	end