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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
$Id$
.Dd August 28, 1993 .Dt SIO 4 i386 .Os FreeBSD .Sh NAME .Nm sio .Nd fast interrupt serial communications interface .Sh SYNOPSIS .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 .Sh DESCRIPTION The .Nm sio driver provides support for NS8250-, NS16450-, and NS16550-based .Tn EIA .Tn RS-232C
f ( Tn CCITT .Tn V.28 ) communications interfaces. The NS8250 and NS16450 have single character buffers, and the NS16550 has a 16 character buffer.
p
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.
.Sh FILES
l -tag -width Pa t Pa /dev/tty00 t Pa /dev/tty01 .El
.Sh DIAGNOSTICS
l -diag t 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 com 4
.Sh HISTORY
The
.Nm
driver is derived from the
.Nm HP9000/300
.Nm dca
driver and is
d .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.
p The constants which define the locations of the various seiral ports are holdovers from .Nm DOS .
p As usual, you get what you pay for; cheap NS16550 clones generally don't work.