write:	mov	al,es:[di]	; al = byte from buffer.
	inc	di		; bump buffer pointer.
	jnz	mwrit2		; hop if no overflow.
	mov	bx,es		; increment segment by 64k.
	add	bx,1000h
	mov	es,bx
mwrit2:	out	data,al		; put byte into controller.
	loop	mwrite		; dec cx, loop until zero.

	; stop controller and wait for next request.
mwexit:	out	intrupt,al	; interrupt controller.
	call	twait		; wait for request and reset.
	ret

	; status phase.
	; exit with al = 0 if no errors.

statphas:
	in	al,status	; al =code,al
	or	al,al			; clear zero flag.
	stc				; set carry flag.
	ret

io_thx:	ret				; return from hard disk r/w routine.


	; Common Teletek hard disk read/write routine.
findalt:
	cld				; set auto = increment.

	mov	ax,hrdtrk		; ax = track number.
	mov	cylind,ax		; cylind = track number.
	mov	ax,hrdsec		; ax = sector requested.
	mov	bl,hrdspt		; bl = sectors per track.
	div	bl			; al = head number.
	mov	mwhead,al		; put head number in cmd buffer.
	mov	mwsectr,ah		; put sector number inrint "HD/CTC does not respond".
	call	prtmsg
	jmp	mwierr			; abort.

	; if got busy and ready together.
move6:	in	al,status		; if controller error.
	test	al,error
	jz	move7			; then
	mov	bx,offset msg1		; print "Load aborted".
	call	prtmsg
	mov	bx,offset msg4		; print "HD/CTC failed self-test".
	call	prtmsg
	jmp	mwierr			; abort.

	; no controller error.
move7:	in	al,data			; read firmware version letter.
	mov	si,offset initdat	; point to initialization data.
	mov	cx,ninbyts		; number bytesbusy		; is it busy?
	jnz	cmnd1		; poll for not busy.
	test	al,ready	; is it ready?
	jz	cmnd1		; poll for ready.

	mov	cx,ncdbyts	; cx = number of command bytes.
	mov	si,offset cmdbuf	; si = command buffer address.
cmndlp:	lodsb			; al = command byte