COM(4)

NAME
com - serial communications interface

SYNOPSIS
# com attachments
#
# i386
com0 at isa? port 0x3f8 irq 4
com1 at isa? port 0x2f8 irq 3
com2 at isa? port 0x3e8 irq 5
com3 at isa? port 0x2e8 irq 9
com* at isapnp?
com* at pcmcia?
com* at puc?
com* at cardbus?

com* at addcom?
com* at ast?
com* at boca?
com* at hsq?

# alpha and amd64
com0 at isa? port 0x3f8 irq 4
com1 at isa? port 0x2f8 irq 3

# amd64 and arm64
com* at acpi?

# arm64 and armv7
com* at fdt?

# hppa
com0 at gsc? offset 0x5000 irq 5
com0 at gsc? offset 0x823000 irq 5
com1 at gsc? offset 0x822000 irq 6
com2 at gsc? irq 13
com1 at dino? irq 11
com0 at ssio? irq 4
com1 at ssio? irq 3

# loongson
com* at leioc?

# macppc
com* at puc?
com* at pcmcia?
com* at cardbus?

# octeon
com* at fdt?

# riscv64
com* at fdt?

# sparc64
com* at asio?
com* at ebus?
com* at puc?

DESCRIPTION
The com driver provides support for NS8250-, NS16450-, NS16550-, ST16650-, ST16C654-, and TI16750-based EIA RS-232C (CCITT V.28) communications interfaces.

The NS8250 and NS16450 have single character buffers, the NS16550 has a 16 character buffer, while the ST16650 has a 32 character buffer, and the TI16750 has a 64 character buffer.

Input and output for each line may be 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, or any other baud rate which is a factor of 115200.

FILES
/dev/tty00
/dev/tty01
/dev/cua00
/dev/cua01

DIAGNOSTICS

com0: N silo overflows The input “silo” has overflowed and incoming data has been lost.

com0: weird interrupt: iir=XXXX The device has generated an unexpected interrupt with the code listed.

SEE ALSO
addcom(4), asio(4), ast(4), boca(4), cardbus(4), dino(4), ebus(4), gsc(4), hsq(4), intro(4), isa(4), isapnp(4), pcmcia(4), puc(4), ssio(4), tty(4)

HISTORY
The com driver was originally derived from the HP9000/300 dca driver.

BUGS
Data loss is possible on busy systems with unbuffered UARTs at high speed.

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