bne	1f / if not, branch
	mov	$511,rcsr(r1) / set control bits for receiver
	mov	$511,tcsr(r1) / set control bits for transmitter
	movb	$210,tty+4(r1) / put 210 in tty table word 3 / set flags
1:
	incb	(r5) / inc first byte of tty buffer
	tst	(sp)+
	tst	u.ttyp / is there a process control tty
	bne	1f / yes, then branch
	mov	r5,u.ttyp / no, make this tty the process control tty
	br	1f / return

ccvt:
	sub	$28.,r1
	asl	r1 / 0%4
	asl	r1
	mov	tty+6(r1),r5
	decb	(r5)
1:
	jmp	sret