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SIO(4)		       FreeBSD Kernel Interfaces Manual			SIO(4)

     sio -- fast interrupt driven asynchronous serial communications interface

     For standard ISA ports:
	   device sio

	   In /boot/device.hints:"isa"

     For AST compatible	multiport cards	with 4 ports:
	   options COM_MULTIPORT
	   device sio

	   In /boot/device.hints:"isa"

     For Boca Board compatible multiport cards with 8 ports:
	   options COM_MULTIPORT
	   device sio

	   In /boot/device.hints:"isa"

     For Netmos	Nm9845 multiport cards with 6 ports:
	   options COM_MULTIPORT
	   device sio

	   In /boot/device.hints:"isa"

     For Hayes ESP cards:
	   options COM_ESP
	   device sio

     For single	port PCI and PCCARD cards:
	   device sio

	   No lines are	required in /boot/device.hints for these cards.

     For dual port PCI cards that share	an interrupt:
	   device sio
	   options COM_MULTIPORT

	   In /boot/device.hints:

     Meaning of	flags:
	   0x00001   shared IRQs
	   0x00002   disable FIFO
	   0x00004   no	AST/4 compatible IRQ control register
	   0x00008   recover sooner from lost output interrupts
	   0x00010   device is potential system	console
	   0x00020   device is forced to become	system console
	   0x00040   device is reserved	for low-level IO (e.g. for remote ker-
		     nel debugging)
	   0x00080   use this port for remote kernel debugging
	   0x0??00   minor number of master port
	   0x10000   PPS timestamping on CTS instead of	DCD
	   0x20000   device is assumed to use a	16650A-type (extended FIFO)

     Minor numbering:

     The sio driver provides support for NS8250-, NS16450-, NS16550 and
     NS16550A-based EIA	RS-232C	(CCITT V.24) communications interfaces.	 The
     NS8250 and	NS16450	have single character buffers, the NS16550A has	16
     character FIFO input and output buffers.

     Input and output for each line may	set to one of following	baud rates;
     50, 75, 110, 134.5, 150, 300, 600,	1200, 1800, 2400, 4800,	9600, 19200,
     28800, 38400, 57600, or 115200.  Your hardware may	limit your baud	rate

     The driver	supports `multiport' cards.  Multiport cards are those that
     have one or more groups of	ports that share an Interrupt Request (IRQ)
     line per group.  Shared IRQs on different cards are not supported.	 Fre-
     quently 4 ports share 1 IRQ; some 8 port cards have 2 groups of 4 ports,
     thus using	2 IRQs.	 Some cards allow the first 2 serial ports to have
     separate IRQs per port (as	per DOS	PC standard).

     Some cards	have an	IRQ control register for each group.  Some cards
     require special initialization related to such registers.	Only AST/4
     compatible	IRQ control registers are supported.  Some cards have an IRQ
     status register for each group.  The driver does not require or use such
     registers yet.  To	work, the control and status registers for a group, if
     any, must be mapped to the	scratch	register (register 7) of a port	in the
     group.  Such a port is called a master port.

     The driver	supports controller based PCI modems.  The 3Com	FaxModem PCI
     and the Advantec 56k Voice	Messaging PCI FaxModem are the only cards sup-
     ported.  WinModems, softmodems, hfc modems	and any	other modems that
     aren't controller based are not supported.

     The flags keyword may be used on each device sio line in the kernel con-
     figuration	file to	disable	the FIFO on 16550A UARTs (see the synopsis).
     Disabling the FIFO	should rarely be necessary.

     The flags keyword must be used for	all ports that are part	of an IRQ
     sharing group.  One bit specifies IRQ sharing; another bit	specifies
     whether the port does not require AST/4 compatible	initialization.	 The
     minor number of the device	corresponding a	master port for	the group is
     encoded as	a bitfield in the high byte.  The same master port must	be
     specified for all ports in	a group.

     The irq specification must	be given for master ports and for ports	that
     are not part of an	IRQ sharing group, and not for other ports.

     In	the synopsis, flags 0x701 means	that the 8th port (sio7) is the	master
     port, and that the	port is	on a multiport card with shared	IRQs and an
     AST/4 compatible IRQ control register.

     flags 0xb05 means that the	12th port (sio11) is the master	port, and that
     the port is on a multiport	card with shared IRQs and no special IRQ con-
     trol register.

     Which port	is the master port depends on the card type.  Consult the
     hardware documentation of your card.  Since IRQ status registers are
     never used, and IRQ control registers are only used for AST/4 compatible
     cards, and	some cards map the control/status registers to all ports in a
     group, any	port in	a group	will sometimes do for the master port.	Choose
     a port containing an IRQ status register for forwards compatibility, and
     the highest possible port for consistency.

     Serial ports controlled by	the sio	driver can be used for both `callin'
     and `callout'.  For each port there is a callin device and	a callout
     device.  The minor	number of the callout device is	128 higher than	that
     of	the corresponding callin port.	The callin device is general purpose.
     Processes opening it normally wait	for carrier and	for the	callout	device
     to	become inactive.  The callout device is	used to	steal the port from
     processes waiting for carrier on the callin device.  Processes opening it
     do	not wait for carrier and put any processes waiting for carrier on the
     callin device into	a deeper sleep so that they do not conflict with the
     callout session.  The callout device is abused for	handling programs that
     are supposed to work on general ports and need to open the	port without
     waiting but are too stupid	to do so.

     The sio driver also supports an initial-state and a lock-state control
     device for	each of	the callin and the callout "data" devices.  The	minor
     number of the initial-state device	is 32 higher than that of the corre-
     sponding data device.  The	minor number of	the lock-state device is 64
     higher than that of the corresponding data	device.	 The termios settings
     of	a data device are copied from those of the corresponding initial-state
     device on first opens and are not inherited from previous opens.  Use
     stty(1) in	the normal way on the initial-state devices to program initial
     termios states suitable for your setup.

     The lock termios state acts as flags to disable changing the termios
     state.  E.g., to lock a flag variable such	as CRTSCTS, use	stty crtscts
     on	the lock-state device.	Speeds and special characters may be locked by
     setting the corresponding value in	the lock-state device to any nonzero

     Correct programs talking to correctly wired external devices work with
     almost arbitrary initial states and almost	no locking, but	other setups
     may benefit from changing some of the default initial state and locking
     the state.	 In particular,	the initial states for non (POSIX) standard
     flags should be set to suit the devices attached and may need to be
     locked to prevent buggy programs from changing them.  E.g., CRTSCTS
     should be locked on for devices that support RTS/CTS handshaking at all
     times and off for devices that don't support it at	all.  CLOCAL should be
     locked on for devices that	don't support carrier.	HUPCL may be locked
     off if you	don't want to hang up for some reason.	In general, very bad
     things happen if something	is locked to the wrong state, and things
     should not	be locked for devices that support more	than one setting.  The
     CLOCAL flag on callin ports should	be locked off for logins to avoid cer-
     tain security holes, but this needs to be done by getty if	the callin
     port is used for anything else.

     /dev/ttyd?	  for callin ports
     /dev/ttyld?  corresponding	callin initial-state and lock-state devices

     /dev/cuaa?	  for callout ports
     /dev/cuala?  corresponding	callout	initial-state and lock-state devices

     /etc/rc.serial  examples of setting the initial-state and lock-state

     The device	numbers	are made from the set [0-9a-v] so that more than 10
     ports can be supported.

     sio%d: silo overflow.  Problem in the interrupt handler.

     sio%d: interrupt-level buffer overflow.  Problem in the bottom half of
     the driver.

     sio%d: tty-level buffer overflow.	Problem	in the application.  Input has
     arrived faster than the given module could	process	it and some has	been

     stty(1), termios(4), tty(4), comcontrol(8)

     The sio driver is derived from the	HP9000/300 dca(4) driver and is	cur-
     rently under development.

     Data loss may occur at very high baud rates on slow systems, or with too
     many ports	on any system, or on heavily loaded systems when crtscts can-
     not be used.  The use of NS16550A's reduces system	load and helps to
     avoid data	loss.

     Stay away from plain NS16550's.  These are	early implementations of the
     chip with non-functional FIFO hardware.

     The constants which define	the locations of the various serial ports are
     holdovers from DOS.  As shown, hex	addresses can be and for clarity prob-
     ably should be used instead.

     Note that on the AST/4 the	card's dipswitches should not be set to	use
     interrupt sharing.	 AST/4-like interrupt sharing is only used when
     multiple AST/4 cards are installed	in the same system.  The sio driver
     does not support more than	1 AST/4	on one IRQ.

     The examples in the synopsis are too vendor-specific.

FreeBSD	9.2			 July 10, 2002			   FreeBSD 9.2


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