Provided by: freebsd-manpages_6.2-1_all bug

NAME
     uart - driver for Universal Asynchronous Receiver/Transmitter (UART)
     devices


SYNOPSIS
     device uart

     device puc
     device uart


DESCRIPTION
     The uart device driver provides support for various classes of UARTs
     implementing the EIA RS-232C (CCITT V.24) serial communications
     interface.  Each such interface is controlled by a separate and
     independent instance of the uart driver.  The primary support for devices
     that contain multiple serial interfaces or that contain other
     functionality besides one or more serial interfaces is provided by the
     puc(4) device driver.  However, the serial interfaces of those devices
     that are managed by the puc(4) driver are controlled by the uart driver.
     As such, the puc(4) driver provides umbrella functionality for the uart
     driver and hides the complexities that are inherent when elementary
     components are packaged together.

     The uart driver has a modular design to allow it to be used on differing
     hardware and for various purposes.  In the following sections the
     components are discussed in detail.  Options are described in the section
     that covers the component to which each option applies.

   CORE COMPONENT
     At the heart of the uart driver is the core component.  It contains the
     bus attachments and the low-level interrupt handler.

   HARDWARE DRIVERS
     The core component and the kernel interfaces talk to the hardware through
     the hardware interface.  This interface serves as an abstraction of the
     hardware and allows varying UARTs to be used for serial communications.

   SYSTEM DEVICES
     System devices are UARTs that have a special purpose by way of hardware
     design or software setup.  For example, Sun UltraSparc machines use UARTs
     as their keyboard interface.  Such an UART cannot be used for general
     purpose communications.  Likewise, when the kernel is configured for a
     serial console, the corresponding UART will in turn be a system device so
     that the kernel can output boot messages early on in the boot process.

   KERNEL INTERFACES
     The last but not least of the components is the kernel interface.  This
     component ultimately determines how the UART is made visible to the
     kernel in particular and to users in general.  The default kernel
     interface is the TTY interface.  This allows the UART to be used for
     terminals, modems and serial line IP applications.  System devices, with
     the notable exception of serial consoles, generally have specialized
     kernel interfaces.


HARDWARE
     The uart driver supports the following classes of UARTs:

     ·   NS8250: standard hardware based on the 8250, 16450, 16550, 16650,
         16750 or the 16950 UARTs
     ·   SAB82532: Siemens SAB 82532 based serial communications controllers
         in asynchronuous mode.
     ·   Z8530: Zilog 8530 based serial communications controllers in
         asynchronuous mode.


FILES
     /dev/ttyu?       for callin ports
     /dev/ttyu?.init
     /dev/ttyu?.lock  corresponding callin initial-state and lock-state
                      devices

     /dev/cuau?       for callout ports
     /dev/cuau?.init
     /dev/cuau?.lock  corresponding callout initial-state and lock-state
                      devices


SEE ALSO
     puc(4)


HISTORY
     The uart device driver first appeared in FreeBSD 5.2.


AUTHORS
     This manual page was written by Marcel Moolenaar 〈marcel@xcllnt.net〉.