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COM(4) Device Drivers Manual COM(4)


comserial communications interface


# 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?
com* at rtfps?

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

# 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?

# sgi
com0 at macebus0 base 0x00390000 irq 5
com1 at macebus0 base 0x00398000 irq 5
com0 at ioc? base 0x00020178
com1 at ioc? base 0x00020170

# socppc
com0 at obio? addr 0x04500 ivec 9
com1 at obio? addr 0x04600 ivec 10

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


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.




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.


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), rtfps(4), ssio(4), tty(4)


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


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.
July 3, 2017 OpenBSD-current