; joystick demonstration for the G7000 by Soeren Gust
; Version 1.3
;
; History:
; Version 1.3
;   The 8048 does not have a Z flag, jz jumps if A=0. So 2 orls were not
;   necessary.
;
; Version 1.2
;   more symbolic names from g7000.h
;
; Version 1.1
;   after changing the shape, i didn't update iram_shape
;   iram_shape gets initialised to 0ffh, so i was setting the shape everytime
;
; Version 1.0
;   first release
;
; This program demonstrates the use of the joystick routines in the g7000
; bios. It also shows how to use the sprite registers. It displays a dot
; which you can move around with the joystick. While moving the dot changes
; into an arrow pointing into the direction it moves. If you press fire it
; doubles its size.

; Copyright (C) 1997 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
iram_shape	equ	024h		; last shape

	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	gfxon		; turn gfx on

	; initialise internal variables
	mov	r0,#iram_xl
	mov	a,#0a0h
	mov	@r0,a
	mov	r0,#iram_xh
	mov	a,#0
	mov	@r0,a
	mov	r0,#iram_y
	mov	a,#080h
	mov	@r0,a
	mov	r0,#iram_shape
	mov	a,#0ffh
	mov	@r0,a

loop
	call	waitvsync	; execute only once per frame
	mov	r1,#0		; joystick 0
	call	getjoystick	; get offsets

	; test, if fire
	mov	r1,#iram_colctrl
	mov	a,#col_spr_white | spr_double
	jf0	firepressed	; fire ?
	mov	a,#col_spr_white
firepressed
	mov	@r1,a		; store color/control

	call	decodejoystick	; get direction from offsets
	call	extramenable	; enable extram
	mov	r0,#07fh	; start of table

	; test, if joystick is in neutral position
	mov	a,r2		; x-offset
	jnz	shapetest	; left/right

	mov	a,r3		; y-offset
	jnz	shapetest	; up/down

	mov	r1,#8		; shape: neutral

shapetest
	; test, if shape has change since last frame
	mov	a,r1		; we need r1 as pointer
	mov	r7,a		; so put contents into r7
	mov	r1,#iram_shape	; last shape
	mov	a,@r1		; get it
	xrl	a,r7		; compare
	jz	setpos		; no need to set shape, skip that part

	; set new value of iram_shape
	mov	a,r7		; the number of the shape
	mov	@r1,a		; put into iram_shape

	; init table to copy shape data
	mov	a,#8		; copy 8 bytes
	movx	@r0,a
	dec	r0
	mov	a,#vdc_spr0_shape
	movx	@r0,a
	dec	r0

	; now copy the data
	mov	a,r7		; number of shape
	rl	a
	rl	a
	rl	a		; 3*rl = a*8
	add	a,#spritedata & 0ffh
	mov	r1,a		; start of shape data
	mov	r7,#8		; 8 bytes
copyspriteloop:
	mov	a,r1
	movp	a,@a		; get byte
	movx	@r0,a		; store in table
	dec	r0
	inc	r1
	djnz	r7,copyspriteloop

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

	; the shapes of the sprite
	; the images are mirrored on the y axis, the VDC prints them on
	; screen that way, so the first shape is the shape for right!!
spritedata:
	db	00000000b
	db	00110000b
	db	01100000b
	db	11111111b
	db	11111111b
	db	01100000b
	db	00110000b
	db	00000000b

	db	11111000b
	db	11100000b
	db	11110000b
	db	10111000b
	db	10011100b
	db	00001110b
	db	00000111b
	db	00000010b

	db	00011000b
	db	00111100b
	db	01111110b
	db	01011010b
	db	00011000b
	db	00011000b
	db	00011000b
	db	00011000b

	db	00011111b
	db	00000111b
	db	00001111b
	db	00011101b
	db	00111001b
	db	01110000b
	db	11100000b
	db	01000000b

	db	00000000b
	db	00001100b
	db	00000110b
	db	11111111b
	db	11111111b
	db	00000110b
	db	00001100b
	db	00000000b

	db	01000000b
	db	11100000b
	db	01110000b
	db	00111001b
	db	00011101b
	db	00001111b
	db	00000111b
	db	00011111b

	db	00011000b
	db	00011000b
	db	00011000b
	db	00011000b
	db	01011010b
	db	01111110b
	db	00111100b
	db	00011000b

	db	00000010b
	db	00000111b
	db	00001110b
	db	10011100b
	db	10111000b
	db	11110000b
	db	11100000b
	db	11111000b

	db	00000000b
	db	00000000b
	db	00000000b
	db	00011000b
	db	00011000b
	db	00000000b
	db	00000000b
	db	00000000b

	end