dc.l $0, start
	dc.l empty_handler
	dc.l empty_handler
	;$10
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$20
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$30
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$40
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$50
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$60
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$70
	dc.l int_4
	dc.l empty_handler
	dc.l int_6
	dc.l empty_handler
	;$80
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$90
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$A0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$B0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$C0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$D0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$E0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	;$F0
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.l empty_handler
	dc.b "SEGA"
empty_handler:
int_6:
	rte
int_4:
	move.w (a2), d0
	ori.w #$8000, d0
	move.w d0, (a4)+
	rte

start:
	lea $C00000, a0
	lea $C00004, a1
	move.w #$8104, (a1) ;Mode 5, everything turned off
	move.w #$8004, (a1)
	move.w #$8220, (a1) ;Scroll a table $8000
	move.w #$8404, (a1) ;Scroll b table $8000
	move.w #$8560, (a1) ;SAT table $C000
	move.w #$8700, (a1) ;backdrop color 0
	move.w #$8B00, (a1) ;full screen scroll
	move.w #$8C81, (a1) ;40 cell mode, no interlace
	move.w #$8C81, (mode).w
	move.w #$8D00, (a1) ;hscroll table at 0
	move.w #$8F02, (a1) ;autoinc 2
	move.w #$9011, (a1) ;64x64 scroll size
	move.l #$C0000000, (a1)
	move.w #$000, (a0)
	move.w #$EEE, (a0)

	;clear scroll table
	move.l #$40000000, (a1)
	move.l #0, (a0)

	;load tiles
	move.l #$44000000, (a1)
	lea font(pc), a2
	move.w #((fontend-font)/4 - 1), d0
tloop:
	move.l (a2)+, (a0)
	dbra d0, tloop



	;clear name table
	move.l #$40000002, (a1)
	moveq #32, d0
	move.w #(64*64-1), d1
ploop:
	move.w d0, (a0)
	dbra d1, ploop


	lea $FF0000, a4
	move.b #$40, (a4, 6)
	move.w #$8144, (a1) ;enable display
	move #$2300, sr

	lea (4, a1), a2 ;hv counter line address
	lea (2, a1), a3 ;second contro/status address

	move.b #254, d0
init_wait:
	cmp.b (a2), d0
	beq init_wait

top:
	move.b #254, d0
	lea $FF0000, a4
	move.w #$8F00, (a1)     ;autoinc of 0
	move.l #$40040000, (a1) ;unused VRAM address
wait_active:
	cmp.b (a2), d0
	bne.s wait_active

	move.l #$8A718014, (a1) ;enable Hints

	;sync to VDP by attempting to fill FIFO
	;being in vblank makes this a bit difficult

	rept 8
	move.l d0, (a0)
	endr

	;sample data for vblank flag off
	rept 82 ;two lines worth of move.l
	move.l (a3), (a4)+
	endr

	move.l a4, a5 ;save end of first buffer

	move.b (a2), d0
wait_new_line:
	cmp.b (a2), d0
	beq.s wait_new_line

	;sync to VDP by filling FIFO
	move.l d0, (a0)
	move.l d0, (a0)
	move.w d0, (a0)

	;sample data for line change HV value
	rept 45 ;one line worth of move.l
	move.l (a2), (a4)+
	endr

	move.l a4, usp ;save end of second buffer

	moveq #$70, d0
wait_hint_line:
	cmp.b (a2), d0
	bne.s wait_hint_line

	;sample data for line change HV value
	rept 45 ;one line worth of move.l
	move.l (a2), (a4)+
	endr

	move.l a4, a6

	move.b #223, d0
wait_inactive:
	cmp.b (a2), d0
	bne.s wait_inactive

	;sync to VDP by filling FIFO
	move.l d0, (a0)
	move.l d0, (a0)
	move.w d0, (a0)

	;sample data for vblank on
	rept 82 ;two lines worth of move.l
	move.l (a3), (a4)+
	endr

	move.l #$8AFF8004, (a1) ;disable Hints

	rsset $FFFF8000
vblank_start_min rs.w 1
vblank_start_max rs.w 1
vblank_end_min   rs.w 1
vblank_end_max   rs.w 1
hblank_start_min rs.w 1
hblank_start_max rs.w 1
hblank_end_min   rs.w 1
hblank_end_max   rs.w 1
line_change_min  rs.w 1
line_change_max  rs.w 1
hint_min         rs.w 1
hint_max         rs.w 1
mode             rs.w 1
printed_hv_dump  rs.b 1
button_state     rs.b 1

	lea $FF0001, a4
.loop:
	btst.b #3, (a4)
	beq.s found_vblank_off
	move.w 1(a4), d6
	addq #4, a4
	bra.s .loop
found_vblank_off:

	move.w (vblank_end_max).w, d0
	beq .new_max
	cmp.w d0, d6
	blo .no_new_max
.new_max
	move.w d6, (vblank_end_max).w
.no_new_max:


	move.w 1(a4), d6

	move.w (vblank_end_min).w, d0
	beq .new_min
	cmp.w d0, d6
	bhi .no_new_min
.new_min
	move.w d6, (vblank_end_min).w
.no_new_min:

	lea $FF0001, a4
;first find a point where HBLANK is not set
	bra.s .start
.loop:
	addq #4, a4
.start
	btst.b #2, (a4)
	bne.s .loop

;then find a point after that where it switches to on
.loop2:
	btst.b #2, (a4)
	bne.s found_hblank_on
	move.w 1(a4), d5
	addq #4, a4
	bra.s .loop2
found_hblank_on:

	move.w (hblank_start_max).w, d0
	beq .new_max
	cmp.w d0, d5
	blo .no_new_max
.new_max
	move.w d5, (hblank_start_max).w
.no_new_max:


	move.w 1(a4), d5

	move.w (hblank_start_min).w, d0
	beq .new_min
	cmp.w d0, d5
	bhi .no_new_min
.new_min
	move.w d5, (hblank_start_min).w
.no_new_min:

;finally find a point after that where it switches back off
.loop2:
	btst.b #2, (a4)
	beq.s found_hblank_off
	move.w 1(a4), d5
	addq #4, a4
	bra.s .loop2
found_hblank_off:

	move.w (hblank_end_max).w, d0
	beq .new_max
	cmp.w d0, d5
	blo .no_new_max
.new_max
	move.w d5, (hblank_end_max).w
.no_new_max:


	move.w 1(a4), d5

	move.w (hblank_end_min).w, d0
	beq .new_min
	cmp.w d0, d5
	bhi .no_new_min
.new_min
	move.w d5, (hblank_end_min).w
.no_new_min:

	move.l a5, a4 ;save line change buffer for later
	move.b (a5), d0
.loop
	move.w (a5), d7
	addq #2, a5
	cmp.b (a5), d0
	beq .loop
found_line_change:

	move.w (line_change_max).w, d0
	beq .new_max
	cmp.w d0, d7
	blo .no_new_max
.new_max
	move.w d7, (line_change_max).w
.no_new_max:

	move.w (a5), d7

	move.w (line_change_min).w, d0
	beq .new_min
	cmp.w d0, d7
	bhi .no_new_min
.new_min
	move.w d7, (line_change_min).w
.no_new_min:

	addq #1, a6
.loop:
	btst.b #3, (a6)
	bne.s found_vblank_on
	move.w 1(a6), d5
	addq #4, a6
	bra.s .loop
found_vblank_on:

	move.w (vblank_start_max).w, d0
	beq .new_max
	cmp.w d0, d5
	blo .no_new_max
.new_max
	move.w d5, (vblank_start_max).w
.no_new_max:

	move.w 1(a6), d5

	move.w (vblank_start_min).w, d0
	beq .new_min
	cmp.b d0, d5
	bhi .no_new_min
.new_min
	move.w d5, (vblank_start_min).w
.no_new_min:

	move usp, a5
.loop:
	btst.b #7, (a5)
	bne.s found_hint
	move.w (a5), d1
	addq #2, a5
	bra.s .loop
found_hint:

	move.w (hint_max).w, d0
	beq .new_max
	cmp.w d0, d1
	blo .no_new_max
.new_max
	move.w d1, (hint_max).w
.no_new_max:

	move.w (a5), d1
	and.w #$7FFF, d1

	move.w (hint_min).w, d0
	beq .new_min
	cmp.b d0, d1
	bhi .no_new_min
.new_min
	move.w d1, (hint_min).w
.no_new_min:

draw_info:
	;draw data
	move.w #$8F02, (a1)     ;autoinc of 2
	move.l #$40840002, (a1)

	moveq #0, d0
	lea VBlankStart(pc), a6
	bsr print_string


	move.w (vblank_start_max), d0
	moveq #0, d1
	bsr print_hexw

	move.w #32, (a0)
	move.w d5, d0
	bsr print_hexw

	move.w #32, (a0)
	move.w (vblank_start_min), d0
	bsr print_hexw

	moveq #0, d0
	move.l #$41040002, (a1)
	lea VBlankEnd(pc), a6
	bsr print_string

	;max value before vblank end
	moveq #0, d1
	move.w (vblank_end_max), d0
	bsr print_hexw

	move.w #32, (a0)
	move.w d6, d0
	bsr print_hexw

	;min value after vblank end
	move.w (vblank_end_min), d0
	move.w #32, (a0)
	bsr print_hexw

	moveq #0, d0
	move.l #$41840002, (a1)
	lea LineChange(pc), a6
	bsr print_string

	move.w (line_change_max), d0
	moveq #0, d1
	bsr print_hexw

	move.w #32, (a0)
	move.w d7, d0
	bsr print_hexw

	move.w (line_change_min), d0
	move.w #32, (a0)
	bsr print_hexw

	moveq #0, d0
	move.l #$42040002, (a1)
	lea HBlankStart(pc), a6
	bsr print_string

	move.w (hblank_start_max), d0
	moveq #0, d1
	bsr print_hexw

	move.w (hblank_start_min), d0
	move.w #32, (a0)
	bsr print_hexw

	moveq #0, d0
	move.l #$42840002, (a1)
	lea HBlankEnd(pc), a6
	bsr print_string

	move.w (hblank_end_max), d0
	moveq #0, d1
	bsr print_hexw

	move.w (hblank_end_min), d0
	move.w #32, (a0)
	bsr print_hexw

	moveq #0, d0
	move.l #$43040002, (a1)
	lea HInterrupt(pc), a6
	bsr print_string

	move.w (hint_max), d0
	moveq #0, d1
	bsr print_hexw

	move.w (hint_min), d0
	move.w #32, (a0)
	bsr print_hexw

	;read pad
	move.b #$40, $A10003
	move.b $A10003, d0
	move.b #$00, $A10003
	and.b #$3f, d0
	move.b $A10003, d1
	and.b #$30, d1
	lsl.b #2, d1
	or.b d1, d0
	not.b d0
	move.b (button_state).w, d2
	eor.b d0, d2
	and.b d0, d2
	move.b d2, d3 ;d3 contains newly pressed buttons, SACBRLDU
	move.b d0, (button_state).w

	btst.l #7, d3
	beq not_pressed

	moveq #0, d0
	move.l d0, (vblank_start_min).w
	move.l d0, (vblank_end_min).w
	move.l d0, (hblank_start_min).w
	move.l d0, (hblank_end_min).w
	move.l d0, (line_change_min).w
	move.l d0, (hint_min).w
	move.b d0, (printed_hv_dump).w
	move.w (mode).w, d0
	eor.w  #$81, d0
	move.w d0, (mode).w
	move.w d0, (a1)
	bra top

not_pressed

	move.b (printed_hv_dump).w, d0
	bne top
	move.b #1, (printed_hv_dump).w

	moveq #0, d1
	moveq #89, d4
	moveq #6, d5
	move.l #$45820002, d6
	move.l d6, (a1)

print_loop:
	dbra d5, .no_line_change
		 ;#$45820002
	add.l #$00800000, d6
	move.l d6, (a1)
	moveq #5, d5
.no_line_change
	move.w #32, (a0)
	move.w (a4)+, d0
	bsr print_hexw
	dbra d4, print_loop

	add.l #$01020000, d6
	move.l d6, (a1)
	moveq #0, d0
	lea Instructions(pc), a6
	bsr print_string

	bra top

VBlankStart:
	dc.b "VBlank Start: ", 0
VBlankEnd:
	dc.b "VBlank End:   ", 0
LineChange:
	dc.b "Line Change:  ", 0
HBlankStart:
	dc.b "HBlank Start: ", 0
HBlankEnd:
	dc.b "HBlank End:   ", 0
HInterrupt:
	dc.b "HInterrupt:   ", 0
Instructions:
	dc.b "Press Start to switch modes", 0

	align 1
;Prints a number in hex format
;d0.w - number to print
;d1.w - base tile attribute
;a0 - VDP data port
;
;Clobbers: d2.l, d3.l
;
print_hexw:
	moveq #3, d3
.digitloop
	rol.w #4, d0
	moveq #$F, d2
	and.b d0, d2
	cmp.b #$A, d2
	bge .hex
	add.w #$30, d2
	bra .makeattrib
.hex
	add.w #($41-$A), d2
.makeattrib
	add.w d1, d2
	move.w d2, (a0)
	dbra d3, .digitloop
	rts

;Prints a null terminated string
;a6 - pointer to string
;a0 - VDP data port
;d0 - base tile attribute
;
;Clobbers: d1.w
print_string:
.loop
	moveq #0, d1
	move.b (a6)+, d1
	beq .end
	add.w d0, d1
	move.w d1, (a0)
	bra .loop
.end
	rts

	align 1
font:
	incbin font.tiles
fontend