INT 61 - Atari Portfolio - FILE TRANSFER SERVICES                               
	AH = 30h
	AL = function
	    00h transmit block
		CX = number of bytes to send
	    01h receive block
		CX = buffer size
	    02h open ports
	    03h close ports
	    04h wait 500ms
	DS:DX -> start of data buffer
Return: DL = status
	    00h successful
	    01h buffer too small
	    02h transmission timeout
	    03h checksum failure
	    04h invalid subfunction
	    05h peripheral not installed
	if function 01h:
	    CX = number of bytes received
SeeAlso: AH=00h"Portfolio",AH=2Eh"Portfolio"