; blink.asm -- resident blink hooked on the display interrupt via the firmware's
; own RAM trampoline at bit 00000DB0h (RLONG(0xFFFFFEA0) = 00000DB0h).
;
; `install` (called by rdebug `jump`, returns) rewrites the 6-byte
; `JA 3F7146D0h` stub to `JA handler`.  `handler` runs on every display
; interrupt, toggles a 64x64 box on the Terminal Manager's white body every
; 0600h invocations, then tail-jumps to the stock OS display handler.
;
; This is the "draw before the OS handler" variant.  If the OS handler repaints
; afterwards, the box will not survive; that is what the frames decide.
;
; Linked at bit 01840000h by dwt/visual/build.sh.

	.text
_start:
	pushst
	dint
	setf	32, 0, 0
	movi	handler, a0, L
	move	a0, @00000DC0h, 0	; stub target
	setf	16, 0, 0
	movi	0C080h, a0, L
	move	a0, @00000DB0h, 0	; JA opcode
	sub	a0, a0
	move	a0, @0186F000h, 0	; counter
	move	a0, @0186F002h, 0	; state (0 = black)
	popst
	rets

handler:
	mmtm	sp, a0,a1,a2,a3,a4,a5
	setf	16, 0, 0
	setf	32, 0, 1
	move	@0186F000h, a0, 0
	inc	a0
	move	a0, @0186F000h, 0
	cmpi	0600h, a0
	jrne	draw
	sub	a0, a0
	move	a0, @0186F000h, 0
	move	@0186F002h, a1, 0
	cmpi	0, a1
	jrne	was_white
	movk	1, a1
	jruc	set_state
was_white:
	sub	a1, a1
set_state:
	move	a1, @0186F002h, 0

draw:
	move	@0186F002h, a1, 0
	cmpi	0, a1
	jrne	pat_white
	sub	a2, a2
	jruc	pat_ready
pat_white:
	movi	0FFFFh, a2, L
pat_ready:
	movi	04064100h, a3, L	; 04000000h + 400*1024 + 256
	movi	64, a4, L
	movi	4, a5, L
drow:
	move	a5, a1
dword:
	move	a2, *a3+, 0
	dsjs	a1, dword
	addi	03C0h, a3
	dsjs	a4, drow

	mmfm	sp, a0,a1,a2,a3,a4,a5
	jauc	3F7146D0h		; stock OS display handler
	.end