; BGSIG - Look for BGii running signature and return info on current task
; Rob Friefeld
; Version 2
; October 3, 1989

; Call BGTASK
; Return NZ = BG not running
; 	  A = 0 if BG not running or upper task
;         A = 20h if lower task 
; Save regs

	public	bgtask
bgtask:
	push	hl
	push	de
	push	bc

	ld	hl,(1)		; Check for BGii
	push	hl
	ld	de,-15a8h	; BG signature offset
	add	hl,de
	ld	b,bgsiglen	; Match string
	ld	de,bgsig
	call	match
	pop	hl
	jr	nz,bgtask1	; Not running
	ld	de,-1602h	; Get pointer to flag byte
	add	hl,de
	ld	e,(hl)
	inc	hl
	ld	d,(hl)
	dec	de
	ld	a,(de)		; Get flags byte
	bit	1,a
	ld	a,20h
	jr	z,bgtask2
	xor	a
bgtask1:
	ld	a,0
bgtask2:
	pop	bc
	pop	de
	pop	hl
	ret
	

bgsig:		db	'BGii'
bgsiglen	equ	$ - bgsig

match:	ld	a,(de)
	cp	(hl)
	inc	hl
	inc	de
	ret	nz
	djnz	match
	ret

	end