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SIO(4)			     Kernel Interfaces Manual			  SIO(4)

NAME
     sio -- fast interrupt driven asynchronous serial communications interface

SYNOPSIS
     For standard ISA ports:
	   device sio

	   In /boot/device.hints:
	   hint.sio.0.at="isa"
	   hint.sio.0.port="0x3f8"
	   hint.sio.0.flags="0x10"
	   hint.sio.0.irq="4"
	   hint.sio.1.at="isa"
	   hint.sio.1.port="0x2f8"
	   hint.sio.1.flags="0x0"
	   hint.sio.1.irq="3"

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

	   In /boot/device.hints:
	   hint.sio.4.at="isa"
	   hint.sio.4.port="0x2a0"
	   hint.sio.4.flags="0x701"
	   hint.sio.5.at="isa"
	   hint.sio.5.port="0x2a8"
	   hint.sio.5.flags="0x701"
	   hint.sio.6.at="isa"
	   hint.sio.6.port="0x2b0"
	   hint.sio.6.flags="0x701"
	   hint.sio.7.at="isa"
	   hint.sio.7.port="0x2b8"
	   hint.sio.7.flags="0x701"
	   hint.sio.7.irq="12"

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

	   In /boot/device.hints:
	   hint.sio.4.at="isa"
	   hint.sio.4.port="0x100"
	   hint.sio.4.flags="0xb05"
	   ...
	   hint.sio.11.at="isa"
	   hint.sio.11.port="0x138"
	   hint.sio.11.flags="0xb05"
	   hint.sio.11.irq="12"

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

	   In /boot/device.hints:
	   hint.sio.4.at="isa"
	   hint.sio.4.port="0xb000"
	   hint.sio.4.flags="0x901"
	   hint.sio.5.at="isa"
	   hint.sio.5.port="0xb400"
	   hint.sio.5.flags="0x901"
	   hint.sio.6.at="isa"
	   hint.sio.6.port="0xb800"
	   hint.sio.6.flags="0x901"
	   hint.sio.7.at="isa"
	   hint.sio.7.port="0xbc00"
	   hint.sio.7.flags="0x901"
	   hint.sio.8.at="isa"
	   hint.sio.8.port="0xc000"
	   hint.sio.8.flags="0x901"
	   hint.sio.9.at="isa"
	   hint.sio.9.port="0xac00"
	   hint.sio.9.flags="0x901"
	   hint.sio.9.irq="12"

     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:
	   hint.sio.2.flags="0x201"
	   hint.sio.3.flags="0x201"

     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 kernel
		     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) chip

DESCRIPTION
     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 char-
     acter 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 choices.

     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.   Frequently  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 regis-
     ter 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 supported.
     WinModems,  softmodems,  hfc  modems and any other modems that are not con-
     troller based are not supported.

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

     The  flags keyword must be used for all ports that are part of an IRQ shar-
     ing group.  One bit specifies IRQ sharing; another  bit  specifies  whether
     the  port does not require AST/4 compatible initialization.  The minor num-
     ber 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 control
     register.

     Which port is the master port depends on the card type.  Consult the  hard-
     ware  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 high-
     est 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  cor-
     responding  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 de-
     vice for each of the callin and the callout "data"  devices.   The  termios
     settings  of  a data device are copied from those of the corresponding ini-
     tial-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  ini-
     tial 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 value.
     E.g., to lock a speed to 115200, use "stty 115200" on the initial-state de-
     vice and "stty 1" on the lock-state device.

     Correct programs talking to correctly wired external devices work with  al-
     most  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 do not support it at all.  CLOCAL should be locked on for de-
     vices that do not support carrier.  HUPCL may be locked off if you  do  not
     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 certain security holes, but
     this needs to be done by getty if the callin  port  is  used  for	anything
     else.

FILES
     /dev/ttyd?       for callin ports
     /dev/ttyd?.init
     /dev/ttyd?.lock  corresponding callin initial-state and lock-state devices

     /dev/cuad?       for callout ports
     /dev/cuad?.init
     /dev/cuad?.lock  corresponding callout initial-state and lock-state devices

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

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

DIAGNOSTICS
     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
     lost.

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

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

BUGS
     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  cannot
     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 proba-
     bly should be used instead.

     Note that on the AST/4 the card's dipswitches should not be set to use  in-
     terrupt  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 sup-
     port more than 1 AST/4 on one IRQ.

     The examples in the synopsis are too vendor-specific.

FreeBSD 8.0			 August 30, 2006			  SIO(4)
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