NAME
	port_handler -- standard serial/parallel/printer port handler.

   SYNOPSIS
	Open("PRT:[RAW/TRANSPARENT/UNIT=<Unit number>]",...);

	Open("SER:[BAUD=<speed>/CONTROL=<settings>/UNIT=<Unit number>]",...);

	Open("PAR:[UNIT=<Unit number>]",...);

   FUNCTION
	Port-handler allows AmigaDOS to interface to a standard parallel
	device, a standard printer device, and a standard serial device.

	Accessing "PAR:" connects AmigaDOS to the system's parallel port.
	By default this will use parallel.device, unit 0. To use a
	different unit number, such as 1, specify "PAR:UNIT=1" instead.

	Accessing "PRT:" connects AmigaDOS to the system's printer. Data
	written to PRT: is processed by the Amiga's printer device, handling
	conversions of ANSI sequences, and sent to the printer. Accessing
	"PRT:RAW" instead causes carriage return translation to be turned
	off in the printer device while printing. To send data transparently
	to the printer, without any translation or escape sequence substitution
	whatsoever, use "PRT:TRANSPARENT". The TRANSPARENT and RAW switches
	are mutually exclusive. By default "PRT:" will access printer.device,
	unit 0. To use a different unit number, such as 1, specify "PRT:UNIT=1"
	instead. The keywords can be combined, such as in "PRT:RAW/UNIT=1".

	Accessing "SER:" connects AmigaDOS to the system's default serial port.
	Following SER:, the baud rate and some control information can be
	supplied. This is done in the form "SER:baud/control" where baud is
	a number indicating the baud rate, and where control is a 3 letter
	sequence denoting the number of read/write bits, the parity, and the
	number of stop bits. For example, "SER:9600/8N1" connects to the
	serial port, sets the baud rate to 9600, with 8 bit data, no parity,
	and 1 stop bit. The possible control settings are:

	        1st character: 7 or 8
	        2nd character: N (No parity), O (Odd parity), E (Even parity)
	                       M (Mark parity), S (Space parity)
	        3rd character: 1 or 2

	Specifying no baud rate or control values when accessing SER: gives you
	the values set in Serial preferences.
	To override the default unit number, use the UNIT keyword, as with the
	PRT: and PAR: devices described above. For example, to access unit 1
	with 38400 bps you could use "SER:38400/UNIT=1".

   PACKETS
	ACTION_FINDINPUT
	ACTION_FINDOUTPUT
	ACTION_FINDUPDATE
	ACTION_READ
	ACTION_WRITE
	ACTION_END
	ACTION_IS_FILESYSTEM

   MOUNTLIST ENTRIES
	dos.library automatically mounts PAR:, PRT:, and SER: upon
	system boot up. The mount entries used by dos.library are equivalent
	to:

	   SER:    Handler   = L:Port-Handler
	           Priority  = 5
	           StackSize = 800
	           GlobVec   = 1
	           Startup   = 0
	   #

	   PAR:    Handler   = L:Port-Handler
	           Priority  = 5
	           StackSize = 800
	           GlobVec   = 1
	           Startup   = 1
	   #

	   PRT:    Handler   = L:Port-Handler
	           Priority  = 5
	           StackSize = 1000
	           GlobVec   = 1
	           Startup   = 2
	   #

	Starting with V40, you can also provide disk-based mount entries
	which let you use port-handler as a serial handler on various devices
	and units. The form of these mount entries is:

	   SER0:   EHandler  = L:Port-Handler
	           Priority  = 5
	           StackSize = 800
	           GlobVec   = 1
	           Device    = serial.device
	           Unit      = 0
	           Flags     = 0
	           Control   = "8N1"
	           Baud      = 9600
	#

	The "Device", "Unit" and "Flags" keywords define the parameters
	that the handler uses for OpenDevice(). "Baud" and "Control"
	define the default values for baud rate and control information for
	whenever that serial handler is accessed by name only, without
	explicit baud rate and control information specified.

   NOTE
	Prior to V40, the baud rate and control information for SER: were
	only recognized if an A2232 multi-serial card was installed in the
	system. Starting with V40, these values are always recognized.

	The TRANSPARENT, UNIT, BAUD and CONTROL keywords were introduced
	with Port-Handler V44. For the different devices, the argument
	templates are:

	    PRT:RAW/S,TRANSPARENT/S,UNIT/K/N
	    SER:BAUD/N,UNIT/K/N,CONTROL/F
	    PAR:UNIT/K/N

	Instead of blank spaces, keywords must be separated by slashes ("/").