COM(4) | Device Drivers Manual | 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`.

December 16, 2021 | Debian