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COM(4)                    OpenBSD Programmer's Manual                   COM(4)

     com, pccom - serial communications interface

     # pccom or com attachments
     # i386
     pccom0 at isa? port 0x3f8 irq 4
     pccom1 at isa? port 0x2f8 irq 3
     pccom2 at isa? port 0x3e8 irq 5
     pccom3 at isa? port 0x2e8 irq 9
     pccom* at isapnp?
     pccom* at pcmcia?
     pccom* at puc?
     pccom* at cardbus?

     pccom* at addcom?
     pccom* at ast?
     pccom* at boca?
     pccom* at hsq?
     pccom* at rtfps?

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

     # 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

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

     # sgi
     com0 at macebus0 sys 0x18 base 0x00390000 irq 5
     com1 at macebus0 sys 0x18 base 0x00398000 irq 5

     # sparc
     com* at obio?                             (built-in modem on SPARCbook)

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

     # zaurus
     com0 at pxaip? addr 0x40100000 intr 22            (full function UART)
     com1 at pxaip? addr 0x40200000 intr 21            (bluetooth UART)
     com2 at pxaip? addr 0x40700000 intr 20            (slow infrared UART)
     com* at pcmcia?

     The com and pccom drivers provide support for NS8250-, NS16450-,
     NS16550-, ST16650-, ST16C654-, and TI16750-based EIA RS-232C (CCITT V.28)
     communications interfaces.  The pccom driver (i386-only) also supports
     the XR16850 UART.

     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.  The XR16850 has a 128 character

     The com and pccom drivers are mutually exclusive; both may not be present
     in the same system at the same time.  Attempting to compile such a system
     will fail.

     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


     com%d: %d silo overflows  The input ``silo'' has overflowed and incoming
     data has been lost.

     com%d: weird interrupt: iir=%x  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), pxaip(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

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

OpenBSD 4.3                      June 20, 2007                               2