COM(4)

NAME
com - serial communications interface

SYNOPSIS
device com0 at isa? port "IO_COM1" tty irq 4 vector comintr
device com1 at isa? port "IO_COM2" tty irq 3 vector comintr
device com2 at isa? port "IO_COM3" tty irq 5 vector comintr
device com3 at isa? port "IO_COM4" tty irq 9 vector comintr

DESCRIPTION
The com driver provides support for NS8250-, NS16450-, and NS16550-based EIA RS-232C (CCITT V.28) communications interfaces. The NS8250 and NS16450 have single character buffers, and the NS16550 has a 16 character buffer.

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.

FILES

/dev/tty00

/dev/tty01

DIAGNOSTICS

com%d: silo overflow. The single-character input “silo” has overflowed and incoming data has been lost.

SEE ALSO
tty(4) sio(4)

HISTORY
The com driver is derived from the HP9000/300 dca driver and is

BUGS
Data loss is possible on busy systems with baud rates greater than 300. The com driver is slow, buggy, and not properly tested.

The name of this driver and the constants which define the locations of the various seiral ports are holdovers from DOS.

As usual, you get what you pay for; cheap NS16550 clones generally don't work.