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34 .Nd driver for Universal Asynchronous Receiver/Transmitter (UART) devices
45 device driver provides support for various classes of UARTs implementing the
46 EIA RS-232C (CCITT V.24) serial communications interface.
47 Each such interface is controlled by a separate and independent instance of
51 The primary support for devices that contain multiple serial interfaces or
52 that contain other functionality besides one or more serial interfaces is
56 However, the serial interfaces of those devices that are managed by the
58 driver are controlled by the
63 driver provides umbrella functionality for the
65 driver and hides the complexities that are inherent when elementary components
66 are packaged together.
70 driver has a modular design to allow it to be used on differing hardware and
72 In the following sections the components are discussed in detail.
73 Options are described in the section that covers the component to which each
79 driver is the core component.
80 It contains the bus attachments and the low-level interrupt handler.
83 The core component and the kernel interfaces talk to the hardware through the
85 This interface serves as an abstraction of the hardware and allows varying
86 UARTs to be used for serial communications.
89 System devices are UARTs that have a special purpose by way of hardware
90 design or software setup.
91 For example, Sun UltraSparc machines use UARTs as their keyboard interface.
92 Such an UART cannot be used for general purpose communications.
93 Likewise, when the kernel is configured for a serial console, the
94 corresponding UART will in turn be a system device so that the kernel can
95 output boot messages early on in the boot process.
98 The last but not least of the components is the kernel interface.
99 This component ultimately determines how the UART is made visible to the
100 kernel in particular and to users in general.
101 The default kernel interface is the TTY interface.
102 This allows the UART to be used for terminals, modems and serial line IP
104 System devices, with the notable exception of serial consoles, generally
105 have specialized kernel interfaces.
113 device driver first appeared in
116 This manual page was written by
117 .An Marcel Moolenaar Aq marcel@xcllnt.net .