COM(4) | Device Drivers Manual | COM(4) |
com
— serial
communications interface for RS-232C
com0 at isa? port "IO_COM1" irq
4
com1 at isa? port "IO_COM2" irq 3
com* at acpi?
com* at cardbus?
com* at isapnp?
com* at mca? slot ?
com* at mhzc?
com* at ofisa?
com* at pcmcia?
com* at pcmcom?
com* at pnpbios? index ?
com* at puc? port ?
com* at xirc?
options COM_HAYESP
options PPS_SYNC
options PPS_TRAILING_EDGE
options RND_COM
com* at clockport?
com0 at mainbus? base 0x00210fe0
com1 at mainbus? base 0x00210be0
com0 at pxaip?
com* at dio? scode ?
com* at frodo? offset ?
com* at dino?
com* at gsc?
com* at ssio?
com* at opb?
com* at ebus?
com* at obio0
com0 at intio0 addr 0xefff00 intr 240
com1 at intio0 addr 0xefff10 intr 241
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, or any other baud rate which is a factor of 115200.
The ttyXX devices are traditional dial-in devices; the dtyXX devices are used for dial-out. (See tty(4).)
options COM_HAYESP
adds support for the
Hayes ESP serial board.
options PPS_SYNC
enables code to use the
Data Carrier Detect (DCD) signal line for attachment to an external
precision clock source (e.g., GPS, CDMA) which generates a Pulse Per Second
(PPS) signal. This is used by
ntpd(8) to discipline the system
clock, and more accurately count/measure time. See
options(4) for more
discussion.
With options RND_COM
enabled, the
com
driver can be used to collect entropy for the
rnd(4) entropy pool. The entropy
is generated from interrupt randomness.
If “flags 1” is specified, the
com
driver will not set the
MCR_IENABLE
bit on the UART. This is mainly for use
on AST multiport boards, where the MCR_IENABLE
bit
is used to control whether or not the devices use a shared interrupt.
acpi(4), ast(4), cardbus(4), i386/pnpbios(4), isa(4), isapnp(4), mca(4), mhzc(4), ofisa(4), options(4), pcmcia(4), pcmcom(4), puc(4), pxaip(4), rtfps(4), tty(4), xirc(4), ntpd(8)
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.
March 4, 2017 | NetBSD 10.99 |