fast interrupt driven asynchronous serial
For standard ISA ports:
For AST compatible multiport cards with 4 ports:
For Boca Board compatible multiport cards with 8 ports:
For Netmos Nm9845 multiport cards with 6 ports:
For Hayes ESP cards:
For single port PCI and PCCARD cards:
No lines are required in /boot/device.hints
for these cards.
For dual port PCI cards that share an interrupt:
Meaning of flags
- shared IRQs
- disable FIFO
- no AST/4 compatible IRQ control register
- recover sooner from lost output interrupts
- device is potential system console
- device is forced to become system console
- device is reserved for low-level IO (e.g. for remote kernel
- use this port for remote kernel debugging
- minor number of master port
- PPS timestamping on CTS instead of DCD
- device is assumed to use a 16650A-type (extended FIFO) chip
driver provides support for NS8250-,
NS16450-, NS16550 and NS16550A-based EIA RS-232C (CCITT V.24) communications
interfaces. The NS8250 and NS16450 have single character buffers, the NS16550A
has 16 character FIFO input and output buffers.
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, 28800, 38400,
57600, or 115200. Your hardware may limit your baud rate choices.
The driver supports `multiport' cards. Multiport cards are those that have one
or more groups of ports that share an Interrupt Request (IRQ) line per group.
Shared IRQs on different cards are not supported. Frequently 4 ports share 1
IRQ; some 8 port cards have 2 groups of 4 ports, thus using 2 IRQs. Some cards
allow the first 2 serial ports to have separate IRQs per port (as per DOS PC
Some cards have an IRQ control register for each group. Some cards require
special initialization related to such registers. Only AST/4 compatible IRQ
control registers are supported. Some cards have an IRQ status register for
each group. The driver does not require or use such registers yet. To work,
the control and status registers for a group, if any, must be mapped to the
scratch register (register 7) of a port in the group. Such a port is called a
The driver supports controller based PCI modems. The 3Com FaxModem PCI and the
Advantec 56k Voice Messaging PCI FaxModem are the only cards supported.
WinModems, softmodems, hfc modems and any other modems that are not controller
based are not supported.
keyword may be used on each
line in the kernel configuration file
to disable the FIFO on 16550A UARTs (see the synopsis). Disabling the FIFO
should rarely be necessary.
be used for all ports that are part of an IRQ sharing group. One bit specifies
IRQ sharing; another bit specifies whether the port does
require AST/4 compatible initialization. The
minor number of the device corresponding a master port for the group is
encoded as a bitfield in the high byte. The same master port must be specified
for all ports in a group.
specification must be given for master
ports and for ports that are not part of an IRQ sharing group, and not for
In the synopsis, flags 0x701
means that the 8th
port (sio7) is the master port, and that the port is on a multiport card with
shared IRQs and an AST/4 compatible IRQ control register.
means that the 12th port (sio11) is the
master port, and that the port is on a multiport card with shared IRQs and no
special IRQ control register.
Which port is the master port depends on the card type. Consult the hardware
documentation of your card. Since IRQ status registers are never used, and IRQ
control registers are only used for AST/4 compatible cards, and some cards map
the control/status registers to all ports in a group, any port in a group will
sometimes do for the master port. Choose a port containing an IRQ status
register for forwards compatibility, and the highest possible port for
Serial ports controlled by the
be used for both `callin' and `callout'. For each port there is a callin
device and a callout device. The minor number of the callout device is 128
higher than that of the corresponding callin port. The callin device is
general purpose. Processes opening it normally wait for carrier and for the
callout device to become inactive. The callout device is used to steal the
port from processes waiting for carrier on the callin device. Processes
opening it do not wait for carrier and put any processes waiting for carrier
on the callin device into a deeper sleep so that they do not conflict with the
callout session. The callout device is abused for handling programs that are
supposed to work on general ports and need to open the port without waiting
but are too stupid to do so.
driver also supports an initial-state
and a lock-state control device for each of the callin and the callout
"data" devices. The termios settings of a data device are copied
from those of the corresponding initial-state device on first opens and are
not inherited from previous opens. Use
in the normal way on the initial-state devices to program initial termios
states suitable for your setup.
The lock termios state acts as flags to disable changing the termios state.
E.g., to lock a flag variable such as CRTSCTS, use
on the lock-state device. Speeds and
special characters may be locked by setting the corresponding value in the
lock-state device to any nonzero value. E.g., to lock a speed to 115200, use
” on the initial-state
device and “
” on the lock-state
Correct programs talking to correctly wired external devices work with almost
arbitrary initial states and almost no locking, but other setups may benefit
from changing some of the default initial state and locking the state. In
particular, the initial states for non (POSIX) standard flags should be set to
suit the devices attached and may need to be locked to prevent buggy programs
from changing them. E.g., CRTSCTS should be locked on for devices that support
RTS/CTS handshaking at all times and off for devices that do not support it at
all. CLOCAL should be locked on for devices that do not support carrier. HUPCL
may be locked off if you do not want to hang up for some reason. In general,
very bad things happen if something is locked to the wrong state, and things
should not be locked for devices that support more than one setting. The
CLOCAL flag on callin ports should be locked off for logins to avoid certain
security holes, but this needs to be done by getty if the callin port is used
for anything else.
- for callin ports
- corresponding callin initial-state and lock-state devices
- for callout ports
- corresponding callout initial-state and lock-state devices
- examples of setting the initial-state and lock-state devices
The device numbers are made from the set [0-9a-v] so that more than 10 ports can
- sio%d: silo overflow.
- Problem in the interrupt handler.
- sio%d: interrupt-level buffer overflow.
- Problem in the bottom half of the driver.
- sio%d: tty-level buffer overflow.
- Problem in the application. Input has arrived faster than the given module
could process it and some has been lost.
driver is derived from the HP9000/300
driver and is currently under development.
Data loss may occur at very high baud rates on slow systems, or with too many
ports on any system, or on heavily loaded systems when crtscts cannot be used.
The use of NS16550A's reduces system load and helps to avoid data loss.
Stay away from plain NS16550's. These are early implementations of the chip with
non-functional FIFO hardware.
The constants which define the locations of the various serial ports are
holdovers from DOS. As shown, hex addresses can be and for clarity probably
should be used instead.
Note that on the AST/4 the card's dipswitches should
be set to use interrupt sharing. AST/4-like
interrupt sharing is only used when multiple
AST/4 cards are installed in the same system. The
driver does not support more than 1
AST/4 on one IRQ.
The examples in the synopsis are too vendor-specific.