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.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Systems Programming Group of the University of Utah Computer
.\" Science Department.
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     from: @(#)dca.4	5.2 (Berkeley) 3/27/91
.\"	from: com.4,v 1.1 1993/08/06 11:19:07 cgd Exp
.\"	$Id: sio.4,v 1.2 1994/02/09 23:49:45 ache Exp $
.\"
.Dd February 9, 1994
.Dt SIO 4 i386
.Os FreeBSD
.Sh NAME
.Nm sio
.Nd
fast interrupt driven asynchronous serial communications interface
.Sh SYNOPSIS
For standard ports:
.Cd "device sio0 at isa? port" \&"IO_COM1\&" tty irq 4 vector siointr
.Cd "device sio1 at isa? port" \&"IO_COM2\&" tty irq 3 vector siointr
.Cd "device sio2 at isa? port" \&"IO_COM3\&" tty irq 5 vector siointr
.Cd "device sio3 at isa? port" \&"IO_COM4\&" tty irq 9 vector siointr
.sp
For multiport cards:
.Cd "options" \&"COM_MULTIPORT\&"
.Cd "device sio4 at isa? port 0x2a0 tty irq 12 vector siointr flags 0x401"
.Cd "device sio5 at isa? port 0x2a8 tty vector siointr flags 0x401"
.Cd "device sio6 at isa? port 0x2b0 tty vector siointr flags 0x401"
.Cd "device sio7 at isa? port 0x2b8 tty vector siointr flags 0x401"
.sp
For bidirectional use of ports:
.Cd "options" \&"COM_BIDIR\&"
.sp
For control FIFO trigger:
.Cd "options" \&"FIFO_TRIGGER=FIFO_TRIGGER_14\&"
.sp
Use 0x02 bit in flags field to disable FIFO on specified port.
.Sh DESCRIPTION
The
.Nm sio
driver provides support for NS8250-, NS16450-, NS16550 and NS16550A-based
.Tn EIA
.Tn RS-232C
.Pf ( Tn CCITT
.Tn V.24 )
communications interfaces.  The NS8250 and NS16450 have single character
buffers, the NS16550A has a 16 character FIFO buffer.
.Pp
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, 38400, 57600, or 115200. Your hardware may limit your baud
rate choices.
.Pp
For multiport cards the 
.Nm flags
keyword in the kernel configuration file determines which port of 
your multiport card is the master device, and whether the 
port is part of a multiport card. The master device is the port which
has register through which all interrupts of the card are funneled.
All ports of a multiport card report pending interrupts using this
single register.
.sp
The master device is indicated 
.Nm bitwise
, so all sio entries in the kernel config file that are part of a 
multiport card must include the correct 
.Nm flags
specification. The bitwise assignment allows multiple multiport cards to
be configured in one system. It does 
.Nm not
imply that the hardware can share the same physical interrupt line!
.Pp
In the synopsis the 
.Nm flags 0x401
means that the 4th port (sio4) is the master
device (so the MSB of the flags), and that the ports are part of a 
multiport card (the LSB of the flags, actually only the LS 
.Nm bit
).
F.e. if you have only two standard ports in addition to multiport
card, this
.Nm flags
will be
.Nm 0x201 .
.Pp
Which port is the master device depends on the card type. Consult
the hardware documentation of your card.
.Pp
Serial ports controlled by the 
.Nm sio
driver can be used for both dialin and dialout. Use 
.Xr comcontrol 8
to enable/disable bidirectional use of the 
.Nm sio
ports. The minor number of the dialout
port is 128 higher than that of the corresponding dialin port. Use 
.Xr stty 1
to enable or disable modem control as required by your setup.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/tty0? for dialin
.It Pa /dev/cua0? for dialout
.El
.Sh DIAGNOSTICS
.Bl -diag
.It sio%d: silo overflow.
The single-character input
.Dq silo
has overflowed and incoming data has been lost.
.\".It com%d: weird interrupt: %x.
.\"The device has generated an unexpected interrupt
.\"with the code listed.
.El
.Sh SEE ALSO
.Xr tty 4 ,
.Xr comcontrol 8 ,
.Xr stty 1 .
.Sh HISTORY
The
.Nm
driver is derived from the
.Nm HP9000/300
.Nm dca
driver and is
.Ud
.Sh BUGS
Data loss is not near as likely on busy systems as they are with the
.Xr com 4
driver but they still can occur at very high baud rates on slow systems. The
use of NS16550A's helps lot to handle high baud rates.
.Pp
Stay away from NS16550 (so without the trailing A). These are early 
implementations of the chip with non-functional FIFO hardware.
.Pp
The constants which define the locations
of the various serial ports are holdovers from
.Nm DOS .
As shown, hex addresses can be and for clarity probably should be used instead.
.Pp
As usual, you get what you pay for; cheap NS16550 clones generally don't work.
.Pp
The multiport example is based on an AST/4 card, your
mileage may vary however. Note that on the AST/4 the card's dipswitches should 
.Nm not
be set to use interrupt sharing. AST/4-like interrupt sharing is only used when 
.Nm multiple
AST/4 cards are installed in the same system. The sio driver does not 
support more than 1 AST/4 on one IRQ.