Format of VINES argument block for Function 0003h subfunction 03h:
Offset	Size	Description	)
 00h	BYTE	session ID (00h)
 01h	BYTE	03h (function "flow control data")
 02h	BYTE	flow control flag
		00h allow characters to be put into display or ring buffer
		01h don't place any more characters into display or ring buffer