title	Module from library BASE_4 : DRVFRE
	name	('DRVFRE')
	maclib	baselib.lib

; Compute disk size in kBytes

; Copyright (C)	Werner Cirsovius
;		Hohe Weide 44
;		D-20253 Hamburg
;		Tel.: +49-40-4223247

;		Version 1.0 February 1988

; ENTRY	Accu holds drive
;	0 -> A ... 15 -> P

; EXIT	Reg pair HL holds 16 bit value of disk free kBytes

;	On normal return carry is reset
;	On error carry will be set and extended error
;	will be processed

	entry	drvfre

	extrn	dsksiz,curdma

drvfre:
	push	bc
	push	de
	call	dsksiz		; Get free space
	push	af		; Save result
	call	curdma		; Get my DMA
	ld	e,(hl)		; Fetch 18 bit
	inc	hl
	ld	d,(hl)
	inc	hl
	ld	a,(hl)
	ex	de,hl
	ld	e,a
	call	div2		; Divide by eight
	call	div2
	call	div2
	pop	af
	pop	de
	pop	bc
	ret
;
; Shift 24bit <E-H-L> right one place
;
div2:
	srl	e		; Shift 18 bit right
	rr	h
	rr	l
	ret

	end