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.\"     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 1.9 1994/03/18 13:40:01 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 flags 0x401 vector siointr"
.Cd "device sio5 at isa? port 0x2a8 tty flags 0x401 vector siointr"
.Cd "device sio6 at isa? port 0x2b0 tty flags 0x401 vector siointr"
.Cd "device sio7 at isa? port 0x2b8 tty flags 0x401 vector siointr"
.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
The driver supports `multiport' cards. 
Multiport cards are those that have one or more groups of ports
that share a common IRQ and Interrupt Request register set per group.
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 seperate IRQs per port
(as per DOS PC standard).
.sp
The
.Nm flags
keyword specifies for each 
.Nm device sio
line in the kernel configuration file, 
whether the port is part of an IRQ sharing group, & if so,
which port is the master device for
the group (ie which port has the IRQ control registers).
The master device is the port which
has registers through which all interrupts of the port group are funneled.
All ports of a port group report pending interrupts using this
single register.
.sp
The master device is an integer embedded in the high byte of the
.Nm flags
bitfield, 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 port groups to
be configured in one system. It does 
.Nm not
imply that more than one port group (or card) can share
the same physical interrupt line!
.Pp
In the synopsis the 
.Nm flags 0x401
means that the 5th 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 
(assuming the control port is 
.Nm sio2
).
.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.
.Pp
While testing new cards & resolving card config DIP header &
.Nm sio flags
settings, to avoid coms. failure from lack of full modem DC level
settings on ports,
you are recommended to temporarily use syntax such as:
.Nm stty -f /dev/tty03 clocal
or open
.Nm /dev/cua03
if you have bidirectional mode active
to force serial port to open without
.Nm O_NONBLOCK
flag.
.Sh FILES
.Bl -tag -width /dev/tty0? -compact
.It Pa /dev/tty0?
for hardwired terminals
.El
or
.Bl -tag -width /dev/tty0? -compact
.It Pa /dev/ttyd?
for dialin ports (and dialout when bidirectional usage disabled)
.It Pa /dev/cua0?
for dialout ports when bidirectional usage enabled
.El
.Pp
The devices numbers are made from the set [0-9a-z] so that more than
10 ports can be supported.
/dev/tty0? and /dev/ttyd? are mutually exclusive, if you have
/dev/tty0? corresponding /dev/ttyd? must be removed and vice versa.
.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.